< 


WITH  COMPLIMENTS  OF 


A  TEXT  -BOOK 


ELEMENTARY  CHEMISTRY 


THEORETICAL  AND  INORGANIC. 


BY  GEORGE  F.  BARKER,  M.  D. 

PROFESSOR  OF  PHYSICS   IN  THE  UNIVERSITY  OF   PENNSYLVANIA. 


Second  Editiou.'Rtvlsesfand  Efr/tirgbd. 


LOUISVILLE,  KY: 

JOHN  P.  MOKTON  AND  COMPANY 

PUBLISHERS. 

1891 


\ 

•/f 


COPYRIGHT,  1891,  BY  JOHN  P.  MORTON  &  COMPANY. 


Eleclrotyped 
BY  ROBERT  ROW  ELL, 

LOUISVILLE,   KY, 


PREFACE  TO  THE  SECOND  REVISED  EDITION. 


The  gratifying  success  achieved  by  the  first  edition  of  this  book 
seems  to  make  it  undesirable,  in  revising  it,  to  alter  materially  its  gen- 
eral plan.  In  this  edition,  therefore,  the  framework  has  been  allowed 
to  remain  in  much  the  same  form  as  that  in  which  it  was  originally 
constructed.  Several  important  changes  of  detail  will  be  noticed, 
however,  among  which  we  may  especially  mention  the  following:  In 
the  first  place,  the  wide-reaching  generalization  of  Mendeleeff,  known 
as  the  periodic  law,  has  been  adopted  throughout.  In  the  earlier  por- 
tion of  the  book  the  law  itself  has  been  discussed  and  illustrated  at 
some  length.  And  in  the  later  portions  its  classifications  -have  been 
made  use  of  in  arranging  the  elements  for  the  purposes  of  study,  and 
the  marvelous  predicting  power  of  the  law  with  reference  to  the 
properties  of  the  elements  has  been  constantly  kept  in  view.  In  the 
second  place,  the  relations  of  the  laws  of  Thermo-chemistry  to  the 
chemical  changes  in  matter,  and  the  importance  of  these  laws  in  the 
elucidation  of  chemical  phenomena,  have  been  clearly  set  forth  in  the 
present  edition,  and  the  intimate  connection  between  matter-changes 
and  energy-changes  in  general  has  been  made  emphatic.  A  third 
change  has  been  made,  which  is  perhaps  a  little  more  radical.  It 
is  the  substitution  of  the  word  "  mass  "  for  "  weight,"  in  the  terms 
"  atomic  weight "  and  "  molecular  weight."  The  word  "  mass  "  in  mod- 
ern physics  always  means  a  quantity  of  matter,  precisely  as  the  word 
"  weight "  always  means  a  quantity  of  force.  And  the  use  of  these 
terms  with  these  exact  meanings  has  been  productive  of  so  much 
clearer  thought  in  physics  as  to  leave  no  doubt  that  a  similar  advan- 
tage will  accrue  to  Chemistry  from  a  similar  use.  True,  mass  in  fact 
is  determined  by  weighing;  but  mass  is  not  weight,  and  the  funda- 
mental idea  of  mass  is  utterly  unlike  that  which  attaches  to  weight. 
Of  course  it  will  not  be  claimed  that  the  term  "atomic  weight"  means 
the  earth's  attraction  on  an  atom,  since  in  that  case  it  would  be  absurd 
to  speak  of  the  atomic  weight  of  hydrogen  as  having  the  same  value 
on  the  fixed  stars  as  on  the  earth,  The  fact  seems  to  be  that  the 

237486  (iii) 


IV  PBEFACE. 

term  "atomic  weight"  is  already  tacitly  used  in  the  sense  of  "atomic 
mass ;"  i.  <?.,  as  meaning  the  quantity  of  matter  which  goes  to  make 
up  an  atom.  Thus  for  example,  Muir  says  in  his  Thermo-chemistry : 
"  The  maximum  atomic  weight  of  an  element  is  the  smallest  mass, 
in  terms  of  hydrogen  as  unity,  of  that  element  in  a  molecule  of  any 
compound  thereof."  But  it  is  precisely  this  use  of  the  word  "  weight" 
which  seems  unfortunate  and  which  it  is  one  of  the  purposes  of  this 
book  to  avoid.  To  use  the  word  '•  weight "  in  the  sense  of  "  mass  "  i.s 
to  introduce  a  vagueness  of  statement  into  the  language  of  science 
which  in  its  effect  must  be  far  more  prejudicial  to  exact  expression 
than  can  ever  be  the  slight  embarrassment  which  rises  from  the  use 
of  the  new  terms  "atomic  mass"  and  "molecular  mass"  until  chem- 
ists shall  have  become  accustomed  to  them.  Moreover  it  will  be 
observed,  I  think,  that  in  the  following  pages  these  terms  fall  into 
place  very  naturally,  and  thus  bring  the  terminology  of  chemistry 
into  entire  accord  with  that  of  the  rest  of  the  physical  domain. 

Lastly,  in  the  present  edition  the  book  has  been  thoroughly  revised 
and  brought  up  to  date;  the  newer  discoveries  in  physical  chemistry, 
such  for  example  as  the  liquefaction  and  solidification  of  the  gases, 
being  recorded  from  the  data  of  the  latest  experiments.  While  there- 
fore a  considerable  amount  of  new  matter  has  been  added,  the  size  of 
the  book  has  not  been  materially  increased.  This  is  important,  since 
in  the  author's  judgment  the  text-book  should  contain  no  more  matter 
than  the  student  may  be  required  to  master;  leaving  to  the  instructor 
the  task  of  amplifying,  explaining,  and  illustrating  the  text.  Rep- 
resenting as  this  book  does  one  of  the  modern  educational  methods 
which  in  the  hands  of  the  author  has  been  found  to  produce  most 
satisfactory  results,  the  new  edition  is  offered  in  the  hope  that  this 
method  may  continue  to  be  successful  and  these  results  continue  to 
be  attained  by  those  of  his  fellow  teachers  who  are  striving  for  a  high 
standard  of  excellence  in  scientific  education. 

PHILADELPHIA,  January,  1891. 


PREFACE  TO  THE  FIRST  EDITION. 


Within  the  past  ten  years  Chemical  science  has  undergone  a  re- 
markable revolution.  The  changes  which  have  so  entirely  altered 
the  aspect  of  the  science,  however,  are  not,  as  some  seem  to  suppose, 
changes  merely  in  the  names  and  formulas  of  chemical  compounds; 
for  in  this  the  science  is  but  returning  to  principles  long  ago  estab- 
lished by  Berzelius.  They  are  changes  which  have  had  their  origin 
in  the  discovery,  first,  that  each  element  has  a  fixed  and  definite  com- 
bining power  or  equivalence;  and  second,  that  in  a  chemical  com- 
pound the  arrangement  of  the  atoms  is  of  quite  as  much  importance 
as  their  kind  or  number.  The  division  of  the  elements  into  groups, 
according  to  the  law  of  equivalence,  necessitated  a  revision,  and  in 
some  cases  an  alteration,  of  their  atomic  weights ;  while,  in  obedience 
to  the  second  law,  molecular  formulas  were  reconstructed  so  as  to 
express  this  atomic  arrangement.  The  importance  of  these  laws  can 
not  be  overestimated.  By  the  former,  all  the  compounds  formed  by 
any  element  may  be  with  certainty  predicted;  by  the  latter,  all  the 
modes  of  atomic  grouping  may  be  foreseen,  and  the  possible  isomers 
of  any  substance  be  pre-determined.  Instead,  therefore,  of  being  a 
heterogeneous  collection  of  facts,  Chemistry  has  now  become  a  true 
science,  based  upon  a  sound  philosophy. 

The  first  part  of  this  book  is  intended  to  be  an  elementary  treatise 
upon  Theoretical  Chemistry.  It  aims  to  present  the  principles  of  the 
science  as  they  are  held  by  the  best  chemists  of  the  day  upon  a  new 
plan  of  treatment  which  the  author  has  found  simple  and  satisfactory 
in  his  own  teaching.  In  studying  it,  it  is  desirable  that  the  student 
commit  to  memory  the  portions  given  in  large  type,  while  the  exam- 
ples given  in  small  type  he  may  recite  in  his  own  language.  These, 
it  must  be  remembered,  are  to  be  extended  by  the  teacher  until  the 
principles  they  illustrate  are  clear  to  every  mind.  The  questions  and 
exercises  printed  at  the  end  of  each  chapter  are  intended  to  be  sug- 
gestive rather  than  exhaustive;  these,  therefore,  should  be  amplified 
by  the  teacher  at  his  discretion.  By  means  of  the  table  on  page  19, 


vi 

the  class  should  be  thoroughly  drilled  in  the  rules  of  naming  chem- 
ical compounds ;  and  by  this  table,  used  in  connection  with  those  on 
pages  16  and  21,  a  very  thorough  drill  in  chemical  notation  may  be 
secured. 

The  second  part  of  the  book  contains  the  facts  of  Inorganic  Chem- 
istry, arranged  systematically  under  appropriate  heads.  To  as  great 
an  extent  as  seemed  desirable,  theory  has  been  applied  to  explain  the 
formation  and  properties  of  compounds.  The  unsatisfactory  classifi- 
cation of  the  elements  into  metals  and  metalloids  is  discarded,  and 
they  are  arranged  electro-chemically,  from  negative  to  positive.  The 
problems  given  in  the  exercises  should  be  conscientiously  worked  out 
by  the  student.  The  metric  system  of  weights  and  measures,  and  the 
centigrade  scale  of  thermometric  degrees  is  used  throughout  the  book. 
Tables  in  the  Appendix  show  the  relation  of  these  measurements  to 
those  of  our  ordinary  standards. 

The  entire  book,  it  is  believed,  is  a  fair  representation  of  the  present 
state  of  Chemical  science.     If  much  appears  in  it  that  is  novel,  much 
more  has  been   omitted  because  unsuited  to  a   strictly  elementary 
book. 
*  *  *  ******  * 

In  conclusion,  this  text-book  is  offered  as  a  contribution  toward 
making  science  disciplinary  as  well  as  instructive.  If  it  be  true  that 
Chemistry  already  excels  in  training  the  powers  of  perception  and  of 
memory,  it  is  unquestionably  true  that  this  science  is  capable  of  devel- 
oping the  reasoning  faculties  also.  The  present  attempt  to  make  it 
available  for  this  purpose,  therefore,  may  fairly  ask  to  be  judged,  not 
in  the  light  of  its  shortcomings  alone,  but  also  by  the  desirability  of 
the  end  at  which  it  aims. 

NEW  HAVEN,  October,  1870. 


TABLE  OF  CONTENTS. 


PART  FIRST:    THEORETICAL  CHEMISTRY. 

CHAPTER  I. — INTRODUCTION.  PA(;E 

Section  1.  Physical  and  Chemical  Properties  of  Matter,        .  1 

CHAPTER  II. — ELEMENTAL  MOLECULES  AND  ATOMS. 

Section  1.  Molecules  in  general, 9 

Section  2.  Elemental  Molecules,          .         .                  .         .  10 
Section  3.  Properties  of  Atoms'     .         .         .        •.         .         .14 

Section  4.  The  Periodic  Law,              23 

Section  5.  Atomic  Notation,  .......  27 

CHAPTER  III. — COMPOUND  MOLECULES. 

Section  1.  Binary  Molecules, 31 

Section  2.  Ternary  Molecules  united  by  Dyads,     ...  39 

Section  3.  Ternary  Molecules  united  by  Triads,         .         .  49 

CHAPTER  IV. — VOLUME-RELATIONS  OF  MOLECULES. 

Section  1.  Relation  of  Density  to  Atomic  Mass,     ...  56 

Section  2.  Relation  of  Gaseous  Diffusion  to  Atomic  Mass,  58 

Section  3.  Combination  by  Volume,        .....  60 

CHAPTER  V. — CHEMICAL  REACTIONS,  STOICHIOMETRY. 

Section  1.  Chemical  Equations, 68 

Section  2.  Stoichiometrical  Calculations,        ....  79 

PART  SECOND:    INORGANIC  CHEMISTRY. 

CHAPTER  I.— HYDROGEN .        .        .  99 

CHAPTER  II. — NEGATIVE  MONADS. 

Section  1.  Chlorine, 107 

Section  2.  Bromine,  Iodine,  and  Fluorine,          .         .         .  116 

Section  3.  Relations  of  the  Halogen  group,   ....  123 

(vii) 


vin 

CHAPTER  III. — NEGATIVE  DYADS. 

Section  1.  Oxygen, 126 

Section  2.  Sulphur, 149 

Section  3.  Selenium  and  Tellurium,   .         .         .         .         .  171 

CHAPTER  IV. — NEGATIVE  TRIADS. 

Section  1.  Nitrogen, .         .170 

Section  2.  Phosphorus,        . 200 

Section  3.  Arsenic  and  Antimony,          .         .         .         .  .      .210 

Section  4.  Bismuth, .         .  218 

Section  5.  Relations  of  the  Nitrogen  group,          .         „         .  221 

CHAPTER  V. — NEGATIVE  TETRADS. 

Section  1.  Carbon,       .         .         : 224 

Section  2.  Silicon, .  251 

CHAPTER  VI. — BORON,  ALUMINUM. 

Section  1.  Boron,         ........  257 

Section  2.  Aluminum, 259 

CHAPTER  VII.— POSITIVE  TETRADS. 

Section  1.  Tin, 264 

Section  2.  Lead, 267 

CHAPTER  VIII.— THE  PLATINUM  GROUP. 

Section  1.  Platinum, 274 

CHAPTER  IX. — THE  IRON  GROUP. 

Sub-group  A.  Chromium, 278 

Sub-group  B.  Manganese, 281 

,.   (Section  1.  Iron, 284 

,b-group  C.  \  Sect.(m  2    N.okcl  Rnd  Cobalt>    .         .         .  293 

CHAPTER  X. — COPPER,  SILVER,  GOLD. 

Section  1.  Copper, 299 

Section  2.  Silver, 302 

Section  3.  Gold, .         .305 

CHAPTER  XI. — GALLIUM,  INDIUM,  THALLIUM. 

Section  1.  Gallium, 308 

Section  2.  Indium, 308 

Section  3.  Thallium,  .  309 


TAIiLK  OF  CONTEXTS.  IX 

CHAPTER  XII.— ZINC,  CADMIUM,  MERCURY. 

Section  1.  Zinc, 311 

Section  2.  Cadmium, 314 

Section  3.  Mercury, •    314 

CHAPTER  XIII. — POSITIVE  DYADS. 

Section  1.  Magnesium,        ..... 

Section  2.  Calcium,          ..... 

Section  3.  Strontium  and  Barium,      ....  324 

CHAPTER  XIV. — POSITIVE  MONADS. 

Section  1.  Lithium,          ......  .    327 

Section  2.  Ammonium, 328 

Section  3.  Sodium, 329 

Section  4.  Potassium, 

Section  5.  Rubidium  and  Caesium,          .....    335 

APPENDIX, 339 

INDEX, 348 


PART  FIRST. 


THEOEETICAL  CHEMISTEY. 


Part  First. 
THEORETICAL  CHEMISTRY. 


CHAPTER    FIRST. 

INTRODUCTION. 
§  1.  PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  MATTER. 

1.  Natural  and  Physical  Science. — Science  is  system- 
atized knowledge  of  nature.     It  is  commonly  divided  into 
Natural  and  Physical  Science. 

Natural  Science  considers  the  external  form  and  the 
internal  arrangement  or  structure  of  natural  objects. 

Physical  Science  concerns  itself  with  the  matter  of 
which  these  objects  are  made  up  and  with  the  energy-changes 
which  this  matter  may  undergo. 

EXAMPLES. — Geology,  Mineralogy,  Botany,  and  Zoology,  which 
treat  of  the  form  and  structure  of  the  earth,  of  minerals,  of  plants, 
and  of  animals,  respectively,  are  called  Natural  Sciences. 

Physics  and  Chemistry,  which  study  the  properties  of  matter 
itself,  whether  hard  or  soft,  heavy  or  light,  combustible  or  non-com- 
bustible, are  called  Physical  Sciences. 

2.  In  studying-  Matter,  Physical  Science  considers : 
1st.  The  divisions  of  which  it  is  capable. 

2d.  The  attractions  by  which  the  divided  particles  are 
held  together. 

3d,    The  motions  which  these  particles  may  have. 

(1) 


2  ^  THEORETIC  A  i;  CHEMISTRY. 

3.  Divisions  of  Matter. — Three  divisions  of  matter  are 
recognized  in  science :  masses,  molecules,  and  atoms. 

A  Mass  of  matter  is  any  portion  of  matter  appreciable  by 
the  senses. 

A  Molecule  is  the  smallest  particle  of  matter  into  which  a 
body  can  be  divided  without  losing  its  identity. 

An  Atom  is  the  still  smaller  particle  produced  by  the 
division  of  a  molecule. 

EXAMPLES. — The  sun  and  the  sand-grain  are  equally  masses  of 
matter.  The  smallest  particles  of  sugar  or  of  salt  which  can  exhibit 
the  properties  of  these  substances,  respectively,  are  molecules  of  sugar 
or  of  salt.  The  still  more  minute  particles  of  carbon,  of  hydrogen,  and 
of  oxygen  which  make  up  the  molecule  of  sugar,  or  those  of  chlorine 
and  of  sodium  which  compose  the  molecule  of  salt,  are  atoms. 

A  mass  of  matter  is  made  up  of  molecules,  and  a  molecule 
itself  is  composed  of  atoms. 

Mass  and  Density. — The  term  mass  is  also  used  to  in- 
dicate the  quantity  of  matter  in  a  body  expressed  in  grams. 
Absolute  density  is  the  mass  of  unit  volume — i.  e.,  the 
number  of  grams  in  one  cubic  centimeter  of  a  substance. 
Relative  density  is  the  ratio  of  the  mass  of  unit  volume  of 
a  given  substance  to  the  mass  of  unit  volume  of  some  stand- 
ard. This,  in  the  case  of  solids  and  liquids,  is  water ;  and 
in  the  case  of  gases,  is  hydrogen.  Since  one  cubic  centime- 
ter of  water  has  the  mass  of  one  gram,  the  absolute  density 
of  a  solid  or  liquid  is  represented  by  the  same  number  as  the 
relative  density.  The  specific  gravity  of  a  gas  is  referred  to 
air  as  unity. 

4.  Attractions  of  Matter. — The  forms  of  matter-attrac- 
tion admitted  in  science  are  three  in  number : 

1st.  That  form  of  attraction  which  is  exerted  between 
masses  of  matter,  called  gravitation. 

2d.  That  which  binds  molecules  together,  called  cohe- 
sion. When  the  molecules  are  unlike,  it  is  frequently  called 
adhesion. 


PHYSICAL    /AT)  CHEMICAL  CHANGED.  3 

3d.  That  which  takes  place  between  atoms,  called  chem- 
ical attraction  or  chemism. 

EXAMPLES. — The  planets  are  held  to  the  sun  and  the  pehble  is  held 
to  the  earth  by  the  attraction  of  gravitation.  The  molecules  of  gold 
or  of  salt  are  held  together  by  cohesive  attraction;  those  in  granite 
or  in  gunpowder  which  are  unlike  are  sometimes  said  to  be  held  to- 
gether by  adhesion.  The  atoms  which  make  up  a  molecule  of  gold  or 
of  .salt  are  united  by  chemical  attraction.  The  nature  of  attraction 
Hself,  however,  is  unknown. 

Like  molecules  Avhen  united  by  cohesion,  form  homogene- 
ous matter ;  unlike  molecules  when  thus  united,  form  hete- 
rogeneous matter.  There  are  as  many  kinds  of  molecules  as 
there  are  kinds  of  homogeneous  matter. 

5.  Motions  of   Matter. — Three  kinds  of  motion  are 
recognized  in  science  : 

1st.   Mass  motion,  or  visible  mechanical  motion. 

2d.  Molecular  motion,  or  the  motion  of  the  molecules 
within  the  mass,  which  is  commonly  called  Heat. 

3d.  Atomic  motion,  or  the  motion  upon  which  spectrum 
analysis  is  assumed  to  rest. 

6.  Province  of   Physics. — Physics  is  that  department 
of  Physical  Science  which  studies  the  results  which  flow  from 
the  molar  and  molecular  conditions  of  matter. 

EXAMPLES. —  Weight,  which  is  a  consequence  of  mass-attraction, 
and  impact,  which  is  a  result  of  muss-motion  ;  tenacity,  hardness,  and 
elasticity,  which  depend  upon  cohesion  ;  and  solution,  capillarity,  and 
diffusion,  which  result  from  adhesion ;  and  the  phenomena  of  heat, 
which  is  a  molecular  motion,  are  all  objects  of  Physical  study  and 
investigation. 

7.  Province  of  Chemistry. — Chemistry,  on   the  other 
hand,  studies  matter  in  its  atomic  condition.     Its  province  is 
to  account  for  the  differences  observed  in  the  various  kinds 
of  homogeneous  matter,  and  to  investigate  the  changes  in  its 
identity  which  this  matter  may  undergo. 

8.  Physical  and  Chemical  changes. — Physical  changes 
in  matter  are  those  which  take  place  outside  the  molecule. 


THEOEETICA  L  CHEMISTR  T. 

They  do  not  affect  the  molecule  itself,  and  therefore  do  not 
alter  the  identity  of  the  matter  operated  on. 

Chemical  changes  take  place  within  the  molecule.  They 
alter  the  character  of  the  molecule,  and  hence  cause  a  change 
iu  the  identity  of  the  matter  itself. 

EXAMPLES. — "Water,  which  is  a  liquid,  may  change  to  iee,  a  solid, 
or  become  steam,  a  gas.  In  all  these  forms,  however,  the  molecule  is 
identically  the  same  ;  these  changes  are  therefore  physical.  But  when 
water  is  subjected  to  the  influence  of  electricity,  it  undergoes  a  more 
radical  change ;  the  water  disappears,  and  in  its  place  appear  two  gas- 
eous substances,  oxygen  and  hydrogen,  with  entirely  unlike  molecules, 
and  hence  with  entirely  different  properties  from  the  water  in  either 
of  its  physical  states.  Such  a  change  as  this  is  a  chemical  change. 

Any  change  in  matter  which  destroys  the  identity  of  the 
substance  acted  on,  is  a  chemical  change.  All  others  are 
physical  changes. 

9.  Physical  and  Chemical  Properties. — Physical  prop- 
erties are  those  which  bodies  possess  in  virtue  of  their  molar 
or  molecular  condition.    Chemical  properties  are  those  which 
are  a  result  of  the  atomic  composition  of  the  molecule. 

EXAMPLES. — Specific  weight,  the  attraction  of  the  earth's  mass  for 
the  unit  of  volume  of  any  body;  tenacity,  which  measures  the 
strength  of  cohesive  attraction;  color,  a  result  of  the  action  of  the 
molecules  of  a  body  upon  light;  physical  state,  depending  upon  the 
character  of  the  molecular  motion.  These  are  examples  of  physical 
properties. 

Combustibility,  explosibility,  capability  of  union  with  and  of  action 
upon  other  bodies,  are  examples  of  chemical  properties. 

10.  Differences  in  Molecules. — Molecules  differ  from 
each  other  because  the  atoms  of  which  they  are  composed  are 
different.     This  difference  may  be : 

1st.   In  kind. 

2d.    In  number. 

3d.    In  relative  position. 

EXAMPLES. — A  molecule  of  salt,  made  up  of  atoms  of  chlorine  and 
of  sodium,  differs  from  a  molecule  of  water,  composed  of  oxygen  and 


l>Kn.\Kf).  5 

of  hydrogen  atoms,  because  the  kind  of  atoms  in  each  molecule  is  dif- 
ferent. A  molecule  of  corrosive  sublimate  and  one  of  calomel  arc  very 
distinct  bodies,  though  both  are  composed  of  atoms  of  mercury  and 
of  chlorine;  the  former  containing  only  half  as  many  mercury  atoms 
as  the  latter  to  the  same  quantity  of  chlorine;  the  difference  in  this 
case  being  due  to  the  number  of  the  component  atoms.  Methyl  ether 
and  ethyl  alcohol,  substances  obviously  different,  contain  in  their 
molecules,  not  only  carbon,  oxygen  and  hydrogen  atoms,  but  pre- 
cisely the  same  number  of  each;  the  differences  in  these  substances, 
therefore,  can  be  due  only  to  a  difference  in  the  relative  position  of 
these  atoms  in  the  molecule  of  each  substance. 

11.  Chemistry  Defined. — Chemistry  is  that  branch 
of  Physical  Science  which  treats  of  the  atomic  compo- 
sition of  bodies,  and  of  those  changes  in  matter  -which 
result  from  an  alteration  in  the  kind,  the  number,  or 
the  relative  position  of  the  atoms  which  compose  the 
molecule. 

TABULAR   RECAPITULATION. 

Sciences.  Divisions.         •      Attractions.  Motions. 

[Masses  Gravitation          Kinetic  Energy. 

Ph>'sics  ( Cohesion 

[  Molecules  Heat. 

(  Adhesion 

Chemistry  Atoms  Chemism  Atomic  Vibration. 

12.  Matter   and    Energy. — Changes   in    matter   neces- 
sarily involve  changes  in  the  energy  with  which  the  matter 
is  associated.     Hence,  although  in  general  the  consideration 
of  energy-transformations  belongs  to  Physics,  yet,  since  purely 
chemical  changes,  such  as  combustion  and  the  like,  involve 
these  transformations,  it  is  evident  that  any  study  of  chem- 
ical phenomena  which  leaves  them  out  of  the  account  would 
be  incomplete.     The  most  important  energy-relations,Mii  the 
chemical  sense,  are  those  which  involve  the  absorption  and 
the  evolution  of  heat,  and  which  constitute,  therefore,,  the 
department  of  Thcrmo-chemistry. 


6  THEORETICAL  CHEMISTRY. 

EXAMPLES. — "When  carbon  burns,  the  amount  of  heat  set  free  is 
perfectly  definite.  Calling  the  quantity  of  heat  required  to  raise  the 
temperature  of  one  gram  of  water  from  0°  to  1°  a  unit  of  heat,  we 
find  that  one  gram  of  carbon  in  burning  produces  8080  units  of  heat. 
Conversely,  to  separate  one  gram  of  carbon  from  its  combuslion-prod- 
uct,  requires  the  absorption  of  8080  heat-units.  Again,  if  one  gram 
of  zinc  be  dissolved  in  sulphuric  acid,  1670  units  of  heat  are  set  free. 
But  if  the  solution  take  place  in  a  voltaic  cell,  the  evolved  energy 
takes  the  form  of  an  electric  current ;  2973  coulombs  being  set  free 
for  each  grain  of  zinc  dissolved. 

-ffither-energy. — But  besides  the  energy  resident  in  mat- 
ter proper,  the  aether  itself  is  a  store-house  of  energy.  Light 
is  aether-vibration  ;  electric  attraction  and  repulsion  are  forms 
of  aether-stress ;  electric  currents  are  due  to  aether-flow,  and 
magnetism  is  aether  vortex-motion. 

13.  Physical  States  of  Matter. — According  to  the  tem- 
perature, matter  exists  in  one  or  another  of  three  distinct 
physical  states,  called,  respectively,  the  solid,  the  liquid,  and 
the  gaseous  states.  There  is  good  reason  to  believe  that  at  a 
sufficiently  high  temperature  all  substances  would  be  gaseous; 
and  at  a  sufficiently  low  temperature,  all  would  be  solid. 
The  point  of  temperature  at  which  a  solid  becomes  a  liquid  is 
called  its  melting-  point ;  and  that  point  at  which,  under  the 
pressure  of  the  atmosphere,  a  liquid  becomes  a  gas  or  vapor 
is  called  its  boiling-  point.  The  number  of  units  of  heat 
required  to  convert  unit  mass  of  a  solid  into  a  liquid  is 
called  its  heat  of  liquefaction ;  and  the  number  required  to 
convert  unit  mass  of  a  liquid  into  gas  or  vapor,  its  heat  of 
vaporization.  The  fraction  of  a  unit  of  heat  required  to 
raise  the  temperature  of  unit  mass  of  any  substance  from  0° 
to  1°  is  called  its  specific  heat. 

EXAMPLES. — Water  cooled  to  0°  becomes  ice,  and  heated  to  100° 
is  converted  into  steam ;  hence,  0°  is  said  to  be  the  melting  point  of 
ice,  and  100°  the  boiling  point  of  water.  When  one  gram  of  ice  is 
melted,  80  units  of  heat  are  absorbed  in  the  process;  and,  conversely, 
when  one  gram  of  water  is  frozen,  80  heat-units  are  set  free.  When 


CRITICAL  TEMPERATURE  AND  PRESSURE.  ( 

one  gram  of  water  at  100°  is  converted  into  steam  at  100°,  heat  corre- 
sponding to  536  units  must  be  supplied  to  it;  and  when  the  one  gram 
of  steam  is  again  condensed,  the  536  heat-units  are  again  set  free. 
One  unit  of  heat  will  raise  the  temperature  of  thirty  units  of  mass  of 
mercury — i.  e.,  thirty  grams  —  from  0°  to  1°.  Hence,  it  will  require 
one  thirtieth  of  a  heat-unit  to  raise  one  gram  from  0°  to  1°.  One 
thirtieth,  or  0-033,  therefore,  is  the  specific  heat  of  mercury. 

14.  Critical  Temperature  and  Pressure. — Physics 
teaches  us  that  at  the  boiling  point  the  pressure  of  a  vapor 
exactly  balances  the  pressure  on  its  liquid  ;  and  hence,  that 
the  boiling  point  is  higher  as  this  pressure  is  greater.  By 
Boyle's  law,  the  density  of  a  vapor  subjected  to  pressure 
steadily  increases,  and  ultimately  becomes  equal  to  that  of 
its  liquid.  Now,  Andrews  has  shown,  on  the  other  hand, 
that  no  amount  of  pressure  will  liquefy  a  gas  unless  the  tem- 
perature at  the  same  time  is  below  a  fixed  point,  which  is 
called  the  critical  temperature.  The  critical  temperature 
is,  therefore,  the  lowest  temperature  which  permits  the  vapor 
to  acquire  the  density  of  the  liquid  without  condensation. 
The  pressure  at  which  this  takes  place,  the  temperature 
being  the  critical  temperature,  is  called  the  critical  press- 
ure. It  is  the  pressure  required  to  liquefy  a  gas  at  the  crit- 
ical temperature.  At  the  critical  point  the  gaseous  and 
liquid  states  are  indistinguishable  from  each  other.  Andrews 
concludes  that  the  one  passes  by  insensible  gradations-  into 
the  other,  and  is  continuous  with  it. 

EXAMPLES.— The  boiling  point  of  water  is  taken  at  100°,  because 
at  this  temperature  its  vapor-pressure  is  760  millimeters,  the  atmos- 
pheric pressure.  If,  however,  the  pressure  on  the  liquid  he  increased 
to  ten  atmospheres,  the  boiling  point  will  rise  to  205°.  At  a  pressure 
of  195-5  atmospheres,  at  370°,  water  vapor  and  liquid  water  have  the 
same  density.  This  pressure  and  this  temperature  are,  therefore,  the 
critical  pressure  and  temperature  for  water.  The  critical  temperature 
and  pressure  for  ammonia  are  130°  and  115  atmospheres;  for  acety- 
lene, 37°  and  68  atmospheres;  for  ethylene,  10-1°  and  51  atmospheres; 
for  marsh-gas,  — 81-8°  and  54-9  atmospheres;  for  oxygen,  — 118°  and 
50  atmospheres. 


THEORETICAL  CHEMISTRY. 


EXERCISES. 

1.  What  is  science? 

2.  How  is  natural  distinguished  from  physical  science? 

3.  Under  which  head  would  astronomy  be  classed? 

4.  Is  physiology  a  natural  or  a  physical  science? 

5.  What  are  the  divisions  of  matter? 

6.  Define  a  molecule  of  water 

7.  What  is  meant  by  the  mass  of  a  body?     What  is  relative 
density? 

8.  Define  gravitation,  cohesion,  chemism. 

9.  What  is  the  difference  between  homogeneous  and  heterogene- 
ous matter? 

10.  Define  mechanical  motion,  heat. 

11.  Are  the  atoms  of  bodies  in  motion? 

12.  What  are  the  objects  of  physical  study?     Illustrate. 

13.  What  is  the  province  of  chemistry? 

14.  Is  the  explosion  of  gunpowder  a  physical  or  a  chemical  change? 

15.  How  are  physical  properties  distinguished  from  chemical? 

16.  Why  is  weight  a  physical  property? 

17.  Why  is  combustion  a  chemical  phenomenon? 

18.  In  what  ways  may  molecules  differ  from  each  other? 

19.  Why  do  water  and  calomel  differ  from  each  other? 

20.  Give  the  definition  of  chemistry. 

21.  What  phenomena  accompany  chemical  changes?     Illustrate 

22.  In  what  three  physical  states  does  matter  exist?     To  what  are 
they  due? 

23.  Define  melting  point,  heat  of  vaporization,  specific  heat. 

24.  What  is  the  critical  temperature  of  a  gas?     Illustrate. 


CLASSIFICATION  OF  MOLECULES. 


CHAPTER   SECOND. 

ELEMENTAL  MOLECULES  AND  ATOMS. 

§  1.     MOLECULES  IN  GENERAL. 

15.  Chemical  Definition  of  Molecule. — A  molecule 
is  a  group  of  atoms  united  by  chemism.     It  is  the  smallest 
particle  of  any  substance  which  exists  in  a  free  or  imcom- 
bined  state  in  nature.  . 

16.  Analysis  and   Synthesis. — The  chemist  ascertains 
the  composition  of  molecules  by  two  methods : 

1st.  By  analysis,  which  consists  in  separating  the  mole- 
cule into  its  constituent  atoms. 

2d.  By  synthesis,  which  consists  in  putting  together  the 
constituent  atoms  to  form  the  molecule. 

17.  Classification   of   Molecules.  —  Molecules  are  di- 
vided into  two  classes : 

1st.   Elemental  molecules,  in  which  the  atoms  are  alike. 

2d.  Compound  molecules,  in  which  the  atoms  are  un- 
like. 

Matter  made  up  of  molecules  containing  like  atoms  is 
called  simple  or  elementary  matter  ;  matter  whose  mole- 
cules are  made  up  of  dissimilar  atoms  is  called  compound 
matter. 

EXAMPLES. — A  mass  of  iron,  of  charcoal,  or  of  sulphur,  is  formed 
of  molecules  whose  atoms  are  alike;  these  substances,  therefore,  are 
examples  of  simple  or  elementary  matter.  The  molecules  which  com- 
pose a  mass  of  glass,  of  marble,  or  of  water,  are  made  up  of  dissimilar 
atoms;  these  substances  are  examples  of  compound  matter.  To  the 
latter  class  by  far  the  larger  number  of  substances  belong. 


10  THEORETICAL  CHEMISTRY. 


§  2.     ELEMENTAL  MOLECULES. 

18.  Mode  of  distinguishing'  Elemental  from  Com- 
pound  Molecules. — Elemental  molecules  may  be   distin- 
guished from  those  which  are  compound  by  causing  a  re- 
arrangement of  the  atoms  between  two  similar  molecules. 
Elemental  molecules,   under  this  treatment,   yield  no  new 
kinds  of  matter  ;   compound  molecules  yield  elemental  mole- 
cules, which,  of  course,  are  different  in  kind. 

EXAMPLES. — Let  act  and  a  a  bo  two  molecules,  each  composed  of 
the  similar  atoms  a;  then  by  re-arrangement  a  a  and  aa  will  be  pro- 
duced, differing  not  at  all  from  the  original  molecules.  If,  however, 
the  molecules  be  ab  and  ab,  composed  of  dissimilar  atoms,  then  by 
re-arrangement  aa  and  bb  are  produced,  both  elemental  molecules.  So, 
ar.  and  ac  would  give  aa  and  cc ;  bd  and  bd,  bb  and  dd. 

From  simple  matter  only  simple  matter  comes ;  but  from 
compound  matter  simple  matter  is  obtained. 

Silver,  oxygen,  copper,  yield  in  this  way  only  silver,  oxygen,  cop- 
per. But  salt  gives  chlorine  and  sodium,  water  gives  oxygen  and 
hydrogen,  blende  gives  zinc  and  sulphur  by  this  re-arrangement. 

19.  Number  of  Elemental  Molecules. — By  effecting 
this  re-arrangement  with  the  molecules  of  all  the  various 
kinds  of  homogeneous  matter  known,  the  number  of  differ- 
ent elemental  molecules  has  been  ascertained.     This  number 
is  probably  about  seventy.     Moreover,  since  every  distinct 
elemental  molecule  is  made  up  of  atoms  peculiar  to  itself,  it 
is  obvious  that  the  number  of  different  kinds  of  atoms  must 
be  about  seventy  also. 

This  is  the  number  at  present  known.  Should  some  new  molecule 
of  compound  matter  be  examined  hereafter,  or  should  some  molecules 
not  now  supposed  compound  be  proved  to  be  so,  others  might  be 
added  to  the  list. 

Of  these  seventy  kinds  of  atoms  all  molecules,  and  there- 
fore all  masses  of  matter,  are  made  up. 


ELEMENTAL  MOLECULES.  11 

20.  Meta-elements. — Recent  researches  have  rendered 
uncertain  the  criteria  hitherto  adopted  for  elementary  bodies, 
and  in  consequence  have  rendered  doubtful  the  number  of 
the  elements.     A  study  of  the  absorption-spectra  of  didym- 
ium  has  shown  that  this  substance  is  capable  of  resolution 
into  nine  separate  components ;  and  yttrium,  by  proper  treat- 
ment, may  be  made  to  yield  five  or  six  constituents,  each 
giving  a  different  phosphorescent  spectrum.     Crookes  con- 
cludes, therefore,  that  substances  like  didymium,  yttrium, 
samarium,   gadolinium,  and  mosandrum,  for  example,   are 
not  actual  chemical  elements,   as  they  have  hitherto  been 
assumed  to  be,  but  are  compounded  of  certain  simpler  bodies, 
which  he  calls,  provisionally,  meta-elements.    Besides  these, 
decipium,  philippium,  holmium,  thulium,  dysprosium,  terbi- 
um, and  gnomium  are  yet  classed  as  doubtful. 

21.  Names  of  Elemental  Molecules  and  Atoms.— 
Both  the  elemental  molecules  and  their  constituent  atoms 
have  the  same  name.    In  many  cases  this  name  is  the  one  by 
which  the  simple  substance  is  familiarly  known.     But  in 
general  the  name  is  given  by  the  discoverer,  either  in  allu- 
sion to  some  special  property  of  the  body  or  to  its  origin  or 
association.     In  a  few  instances  the  names  are  fancifuL 

EXAMPLES.— The  name  gold  is  applied  equally  to  the  molecules 
which  make  up  the  mass  and  to  the  atoms  which  form  the  molecule. 
This  name,  like  that  of  lead,  tin,  or  iron,  is  the  name  of  the  substance 
in  common  use. 

Chlorine,  a  greenish-yellow  gas,  gets  its  name  from  ^/Iwpdf,  greenish- 
yellow.  Hydrogen  comes  from  ikfwp,  water,  and  yevvdu,  I  produce, 
because  it  generates  water  by  its  combustion.  Calcium  conies  from 
calx,  lime,  because  it  is  obtained  from  that  substance.  Caesium  is 
from  ccesius,  sky-blue,  because  there  are  two  bright  blue  lines  in  its 
spectrum.  Cerium,  palladium,  and  uranium  are  named  from  the  cor- 
responding planets.  And  titanium  and  tantalum  from  mythological 
deities. 

(A.  list  of  the  simple  substances  now  known,  with  the  derivation  of 
their  names  and  the  names  of  their  discoverers,  is  given  in  the  ap- 
pendix.) 


12  THEORETICAL  CHEMISTRY. 

22.  Size  and  Mass  of   Elemental  Molecules. — Ac- 
cording to  the  law  of  Avogadro  (1811)  or  Ampere  (1814), 
equal  volumes  of  all  substances  in  the  gaseous  state  contain 
the  same  number  of  molecules.     From  which  it  follows : 

1st.  That  the  molecules  of  all  substances,  when  in  the 
gaseous  state  are  of  the  same  size. 

2d.  That  the  mass  of  any  molecule,  compared  with  that 
of  hydrogen,  is  proportional  to  the  mass  of  any  given  vol- 
ume also  compared  with  the  same  volume  of  hydrogen. 

EXAMPLES. — If  one  liter  of  oxygen — the  mass  of  which  is  16  times 
as  great  as  that  of  a  liter  of  hydrogen — contains  the  same  number  of 
molecules,  then  it  is  obvious  that  the  mass  of  each  molecule  of  oxygen 
must  be  16  times  the  mass  of  a  molecule  of  hydrogen.  If  the  relative 
density  of  nitrogen  be  14,  the  mass  of  a  molecule  of  nitrogen  must 
be  14  times  that  of  a  molecule  of  hydrogen. 

23.  Number  of  Atoms  in  the  Hydrogen  Molecule. — 

Assuming  that  one  volume  of  hydrogen  contains  1000  mole- 
cules, then  by  Avogadro's  law,  one  volume  of  chlorine  will 
contain  1000  molecules  also.  If  these  volumes  be  mixed 
together  and  exposed  to  sunlight,  they  combine  to  form  two 
volumes  of  a  new  substance- — hydrochloric  acid  gas — which 
two  volumes,  of  course,  by  the  same  law,  will  contain  2000 
molecules.  Upon  analysis,  each  molecule  of  hydrochloric 
acid  gas  is  found  to  consist  of  two  atoms,  one  of  hydrogen, 
the  other  of  chlorine.  The  2000  molecules,  therefore,  will 
contain  2000  hydrogen-atoms  and  2000  chlorine-atoms ;  but 
the  2000  hydrogen-atoms  came  from  the  1000  molecules  in 
the  original  volume,  and  the  2000  chlorine-atoms  came  from 
the  1000  chlorine  molecules.  Each  molecule  of  hydrogen 
must,  therefore,  have  furnished  two  hydrogen-atoms ;  and 
each  molecule  of  chlorine,  two  chlorine-atoms.  Hence,  a 
molecule  of  hydrogen  is  made  up  of  two  atoms. 

24.  Molecular  Masses. — If  the  mass  of  the  hydrogen 
atom  be  taken    as   1,  then,  since  its  molecule  contains  two 
atoms,  its  molecular  mass  will  be  2.     The  molecular  mass  of 


KLEM  ENTA  L  MOL  EC  VL  ES. 


13 


any  other  substance  may  be  obtained  by  multiplying  its 
relative  density  in  the  state  of  gas,  by  the  molecular  mass 
of  hydrogen. 

EXAMPLES. — The  relative  density  of  nitrogen  gas,  for  example,  is 
14;  that  is,  a  given  volume  of  it— say  one  liter — has  14  times  the  mass 
of  one  liter  of  hydrogen.  Its  moleeule  must,  therefore,  have  14  times 
the  mass;  and  si/ice  the  molecular  mass  of  hydrogen  is  2,  the  molecu- 
lar mass  of  nitrogen  is  14x2;  that  is,  28.  Again,  the  relative  den- 
sity of  phosphorus  vapor  is  62;  its  molecular  mass  is  62x2,  or  124. 

25.  Number  of  Atoms  in  Elemental  Molecules. — 

The  number  of  atoms  in  any  elemental  molecule  is  obtained 
by  dividing  the  molecular  mass  by  the  atomic  mass. 

EXAMPLES. — The  molecular  mass  of  nitrogen  being  28,  and  its 
atomic  mass — obtained  by  a  method  to  be  described  hereafter — 14,  the 
number  of  atoms  in  its  molecule  is  28  —  14,  or  2.  The  molecular  mass 
of  phosphorus  being  124,  and  its  atomic  mass  31,  its  molecule  must 
contain  four  atoms. 

2G.  Atomicity  of  Elemental  Molecules.  —The  atom- 
icity of  a  molecule  is  the  number  of  atoms  which  it  contains. 
Molecules  are  mon-atomic,  di-atomic,  tri-atomic,  tetr-atomic, 
or  hex-atomic,  according  as  they  contain  one,  two,  three,  four, 
or  six  atoms.  Most  elemental  molecules  are  di-atomic. 

(Many  simple  substances,  not  being  volatile,  can  not  be  weighed  in 
the  gaseous  state.  They  are  usually  classed  as  di-atomic,  however, 
their  di-atomicity  being  assumed.) 

Those  elemental  molecules  whose  atomicity  has  been  exper- 
imentally determined,  are  given  in  the  following  table : 


Kfon-dtomic. 

Di-atomic, 

Tri-atomic. 

Teir-atomic.      Hex-atomic. 

Mercury 

Hydrogen 

Oxygen 

Phosphorus         Sulphur 

Cadmium 

Oxygen 

(as  ozone) 

Arsenic              (about  550°) 

Zinc 

Fluorme 

Selenium 

Barium  (?) 

Chlorine 

(below  800°) 

Iodine 

Bromine 

(at  ir>00  ) 

Iodine 

Bromine 

(below  1000°) 

(at  1800  ') 

Nitrogen 

Sulphur 

(above  800') 

Selenium 

(above  lilixn 

Tellurium 

k 

14  THEORETICAL  CHEMISTRY. 

Since  all  molecules  are  of  the  same  size,  molecular  atomic- 
ity may  be  thus  represented  : 


000 


§3.    PROPERTIES  OF  ATOMS. 

27.  Definition  of  Atom. — An  atom  is  the  smallest  par- 
ticle of  simple  matter  which  enters  into  the  composition  of  a 
molecule. 

28.  Classification  of  Atoms. — Atoms  differ  from  each 
other : 

1st.   In  mass. 

2d.    In  the  quality  of  their  combining  power. 

3d.    In  the  quantity  of  their  combining  power. 

29.  Atomic  Mass. — The  relative  mass  of  any  atom  re- 
ferred to  that  of  the  atom  of  hydrogen  as  unity  is  its  atomic 
mass.     It  is  the  smallest  mass  of  any  simple  substance  which 
actually  takes  part  in  the  formation  of  any  chemical  com- 
pound. 

30.  Method  of  fixing-  the  Atomic  Mass. — In  order  to 
fix  an  atomic  mass  we  must  know  : 

1st.  The  relative  mass  of  the  substance  which  combines 
with  one  unit  of  mass,  i.  e.,  one  atom  of  hydrogen. 

2d.    The  molecular  mass  of  the  hydrogen  compound. 

I.  Analysis  of  the  compound  which  any  element  forms  with 
hydrogen  will  give  the  absolute  mass  of  each  constituent  in 
any  given  quantity — say  100  grams.  The  mass  of  the  body 
which  unites  with  unit  mass  of  hydrogen  may  then  be  ob- 
tained by  a  simple  proportion. 

EXAMPLES. — Analysis  shows  that  hydrochloric  acid  gas — the  hy- 
drogen compound  of  chlorine — contains,  in  100  grams,  97-26  grams  of 
chlorine  and  2-74  grams  of  hydrogen.  By  the  proportion  2-74  :  97-26 
:  :  1  :  35-5,  it  is  ascertained  that  in  this  compound  the  quantity  of 


PROPERTIES  OF  ATOMS.  15 

chlorine  which  combines  with  unit  mass — i.  e.,  one  atom  of  hydrogen — 
has  a  mass  35-5  times  as  great. 

Again,  the  analysis  of  water  shows  it  to  be  composed  of  88'89  per 
cent  of  oxygen  and  11-11  per  cent  of  hydrogen;  whence  11-11  :  88-8'J 
:  :  1  :  8.  Eight  parts  of  oxygen  unite  with  one  part  of  hydrogen. 

So  ammonia  gas  contains  in  100  parts,  82-35  parts  of  nitrogen  and 
17-65  parts  of  hydrogen ;  or  17-65  :  82-35  :  :  1  :  4-7.  Hence,  4-7  parts 
of  nitrogen  combine  with  1  part  of  hydrogen. 

Now,  if  in  a  molecule  of  hydrochloric  acid,  water,  or  ammonia 
there  is  but  one  atom  of  hydrogen,  then  35-5,  8,  and  4-7,  being  the  small- 
est musses  of  chlorine,  oxygen,  and  nitrogen  which  combine,  will  be 
the  atomic  masses  of  these  bodies  respectively. 

II.  The  molecular  mass  of  any  substance  is  the  sum  of 
the  masses  of  its  constituent  atoms.  The  combining  masses 
obtained  by  analysis,  when  added  together,  therefore,  must 
give  either  the  molecular  mass  or  some  number  of  which  the 
molecular  mass  is  a  multiple.  In  this  way  the  number  of 
hydrogen  atoms  in  the  compound  may  be  determined ;  and 
the  mass  of  the  other  constituent  which  is  united  with  these 
hydrogen  atoms  is  its  atomic  mass. 

EXAMPLES. — The  relative  density  of  hydrochloric  acid  gas,  of 
steam,  and  of  ammonia  gas,  respectively,  is  18-25,  9,  and  8-5;  their 
molecular  masses,  therefore,  are  36-5,  18,  and  17.  The  sum  of  the 
combining  masses  of  hydrogen  and  chlorine,  obtained  by  analysis 
(35-5-f- 1),  is  36-5.  But  this  is  the  molecular  mass  of  hydrochloric  acid 
gas.  Hence  one  molecule  of  this  gas  contains  one  atom  of  chlorine 
and  one  of  hydrogen,  and  the  atomic  mass  of  chlorine  is  35-5. 

Again,  the  sum  of  the  combining  masses  of  oxygen  and  hydrogen 
(8-(-l)  is  9.  But  9  is  one  half  the  molecular  mass  of  water;  hence,  a 
molecule  of  water  contains  twice  as  much  of  each  constituent — i.  e., 
2  parts  of  hydrogen  and  16  of  oxygen.  16  is,  therefore,  the  atomic 
mass  of  oxygen. 

So,  if  the  combining  masses  of  nitrogen  and  hydrogen  be  added 
together,  the  sum  is  (4-7-f  1 )  5-7.  But  5-7  is  only  one  third  the  molec- 
ular mass  of  ammonia,  which  is  17.  Ammonia,  therefore,  contains 
three  times  as  much  hydrogen  and  nitrogen  in  one  molecule  as  the 
smallest  value  given  by  analysis.  It  must  contain,  therefore,  3  parts 
of  hydrogen  and  14  (4-7X3)  parts  of  nitrogen;  and  the  atomic  mass 
of  nitrogen  is  fixed  at  14. 


16 


THEORETICAL  CHEMISTRY. 


ELEMENTAL  SYMBOLS  AND  ATOMIC  MASSES. 


Symbol. 

At.  mass. 

Symbol. 

At.  mass. 

Hydrogen 

H 

1 

Chromium                  Cr 

52-45 

Fluorine 
Chlorine 

F 
01 

19-06 
3537 

Molybdenum             Mo 
Tungsten  (  Wolfram)V? 
Uranium                     U 

95-9 
183-6 
2398 

Bromine 

Br 

79-76 

Iodine 

I 

126-54 

Osmium                       Os 

191-0 

Iridiiim                        Ir 

1925 

Oxygen 

0 

15-96 

Platinum                     Pt 

194-3 

Sulphur 

s 

31-98 

Selenium 

Se 

78-87 

Ruthenium                Ru 

103-5 

Tellurium 

Te 

125-00 

Rhodium                    Ro 

1041 

Palladium                  Pd 

1062 

Nitrogen 

N 

14-01 

Phosphorus 

P 

3096 

Iron  (Fcrrum)          Fe 

55-88 

Arsenic 

As 

71-9 

Nickel                        Ni 

58-50 

Antimony  (Stibium)Sb 

119-6 

Cobalt                         Co 

58-74 

Bismuth 

Bi 

207-3 

Manganese                Mn 

54-8 

Carbon 

C 

11-97 

Gallium                      Ga 

69-9 

'Silicon 

Si 

280 

Indium                        In 

113-4 

Titanium 

Ti 

48-0 

Thallium                    Tl 

203-7 

Zirconium 

Zr 

90-4 

Cerium 

Ce 

141-2 

Copper  (Cuprum)     Cu 

63-4 

Thorium 

Th 

232-4 

Silver  (Argention)    Ag 

107-G6 

Boron 

B 

10-95 

Gold  (Aurunt)           An 

196-7 

Aluminum 

Al 

27-04 

Zinc                             Zn 

64-9 

Scandium 

Sc 

44-04 

Cadmium                    Cd 

111-7 

Yttrium 

Y 

89-6 

Mercury  (Hydrar- 

Lanthanum 

La 

138-5 

gyrum}                Hg 

199-8 

Ytterbium 

Yb 

172-6 

Beryllium                  Be 

9-08 

Vanadium 

V 

51-2 

Magnesium                 Mg 

23-94 

Columbian! 

Ob 

93-7 

Calcium                       Ca 

3991 

Didymium 
Tantalum 

Di 
Ta 

142-1 
182-0 

Strontium                   Sr 
Barium                       Ba 

87-3 
136-9 

Erbium                        E 

166-0 

Germanium 

Ge 

7332 

Lithium                      Li 

7-01 

Tin  (Stannum) 
Lead  (Plumbum) 

Sn 
Pb 

1178 
206-4 

Sodium  (Natrium)   Na 
Potassium  (  Kalium]  K 

23-0 

39-03 

Rubidium                    Rb 

852 

Caesium                       Cs 

132-7 

ATOMIC  MASS.  17 

31.  Indirect  Methods  of  Fixing'  Atomic  Masses. — 

In  some  cases  elements  do  not  unite  directly  with  hydrogen. 
The  comparison  with  hydrogen  is  then  made  by  means  of  a 
middle  term,  generally  chlorine. 

EXAMPLES. — No  hydrogen  compound  of  silver  is  known.  But  sil- 
ver combines  with  chlorine  to  form  the  well-known  ore,  horn-silver. 
On  analysis,  this  horn-silver  yields  75-2G  per  cent  of  silver  and  24-74 
per  cent  of  chlorine.  As  35  5  parts  of  chlorine  combine  with  one  of 
hydrogen,  the  quantity  of  silver  which  combines  with  85-5  parts  of 
chlorine  is  its  atomic  mass,  24-74  :  75-26  :  :  35-5  :  108,  the  atomic  mass 
of  silver. 

32.  Atomic  Heat. — Dulong  and  Petit  (1819)   pointed 
out  the  fact  that  the  product  of   the  specific  heat  by  the 
atomic  mass  is  constant  for  nearly  all  the  elements  ;  or,  what 
is  the  same  thing,  the  specific  heat  of  an  element  is  inversely 
proportional  to  its  atomic  mass.      This  constant  product  is 
called  the  atomic  heat ;  and,  since  it  has  the  same  value  for 
all  the  elements,  it  follows  that  the  specific  heat  of  all  atoms 
is  the  same.     Since  the  average  value  of  this  product  is  6*4, 
it  is  evident  that  the  atomic  mass  of  an  element  may  be  ap- 
proximately obtained  by  dividing  6'4  by  the  specific  heat  of 
the  element. 

(The  exact  atomic  masses  of  the  best-known  elements  are 
given  on  the  opposite  page.) 

33.  Quality  of   Atomic  Combining'  Power. — Atoms 
are  divided  into  two  classes,  according  to  the  quality  of  their 
combining  power.     These  are  : 

1st.  Positive  atoms,  or  those  which  are  attracted  to  the 
negative  electrode  in  electrolysis,  and  whose  hydroxides  are 
bases. 

2d.  Negative  atoms,  or  those  which  go  to  the  positive 
electrode,  and  whose  hydroxides  are  acids. 

EXAMPLES. — Salt,  under  the  influence  of  electricity,  is  decomposed 
into  chlorine  and  sodium.  The  chlorine  atoms  collect  at  the  positive 
electrode,  and  are  therefore  called  negative.  The  sodium  atoms  are 


18  THEORETICAL  CHEMISTRY. 

found  at  the  negative  electrode,  and  are  hence  called  jyositive.  Again, 
all  the  hydroxides  of  chlorine  are  acids,  while  the  hydroxides  of  so- 
dium and  potassium  — substances  like  chlorine  in  all  other  chemical 
characters — are  entirely  different  bodies,  called  bases. 

In  the  table  on  the  next  page  the  more  common  elements 
are  arranged  according  to  their  electro-chemical  characters, 
each  atom  being  positive  to  any  atom  which  is  placed  above 
it,  and  negative  to  any  one  given  below  it.  These  distinc- 
tions, although  entirely  relative,  are  yet  important,  since 
upon  them  rest  not  only  the.  principles  of  chemical  nomen- 
clature and  notation,  but  also,  as  seems  probable,  the  nature 
of  chemical  attraction  itself. 

34.  Quantity  of  Atomic  Combining-  Power. — If  the 
combining  power  of  the  atom  of  hydrogen  be  taken  as  1, 
the  combining  power  of  other  atoms  will  be  1,  2,  3,  4,  5,  6 
or  7.  That  is,  some  atoms  have  a  combining  power  equal  to 
that  of  hydrogen  and  can  unite  with  one  atom  of  it.  Other 
atoms  have  a  higher  combining  power  and  can  unite  with  2, 
3,  4,  5,  6  or  7  hydrogen  atoms  or  their  equivalents.  Quan- 
tity of  combining  power  should  not,  however,  be  confounded 
with  intensity  of  combining  power. 

EXAMPLES. — Atoms  combine  with  other  atoms  in  virtue  of  their 
chemism,  an  attraction  mutually  satisfied  by  the  union.  Taking 
the  chemism  of  an  atom  of  hydrogen  as  the  unit,  any  other  atom  whose 
chemism  is  completely  satisfied  by  uniting  with  the  hydrogen-atom, 
is  its  equal  in  the  quantity  of  its  combining  power.  Other  atoms 
there  are,  whose  chemism  requires  for  saturation,  two,  three,  four,  five, 
six,  or  seven  hydrogen-atoms;  hence  the  quantity  of  their  combining 
power — which  is  the  same  for  all  other  similar  atoms — is  said  to  be 
one,  two,  three,  four,  five,  six,  seven. 

A  chlorine-atom  is  completely  satisfied  with  one  atom  of  hydrogen  ; 
but  an  oxygen-atom  requires  two,  a  nitrogen-atom,  three,  a  carbon- 
atom,  four,  and  so  on.  This  is  entirely  consistent  with  the  fact  that 
the  intensity  of  the  attraction  between  hydrogen  and  chlorine  atoms 
is  greater  than  that  which  either  hydrogen  or  chlorine  atoms  have  for 
each  other. 


ELECriiO-CHKMICAL  SERIES.  19 


Negative  End  —  Oxygen. 
Sulphur. 
Nitrogen. 
Fluorine. 
Chlorine. 
Bromine. 
Iodine. 
Selenium. 
Phosphorus. 
Arsenic. 
Chromium. 
Vanadium. 
Molybdenum. 
Tungsten. 
Boron. 
Carbon.  — • 
Antimony. 
Tellurium. 
Tiintalnm. 
Columbium. 
Titanium. 
Silicon. 
Tin. 

Hydrogen. 
Gold. 
Osmium. 
Iridium. 
Platinum. 
Rhodium. 
Ruthenium. 
Palladium. 
Mercury. 
Silver. 
Copper. 
Uranium. 
Bismuth. 
Gallium. 
Indium. 
Germanium. 
Lead.  - 
Cadmium. 
Thallium. 
Cobalt. 
Nickel. 
Iron. 
Zinc. 

Manganese. 
Lanthanum. 
Didymium. 
Cerium. 
Thorium. 
Zirconium. 
Aluminum. 
Scandium. 
Erbium. 
Yttrium. 
Ytterbium. 
Beryllium. 
Magnesium. 
Calcium. 
Strontium. 
Barium. 
Lithium. 
Sodium.    - 
Potassium. - 

r,     -j .      r>   j    t     Rubidium. 
rositive  E,na  -j-  Caesium. 


20  THEOItKTH'AL  CIIKMISTRY. 

35.  Valence. — The  valence  of  an  atom  in  any  case  is 
the  quantity  of  its  combining  power,  expressed  in  hydrogen 
units.     Since  the  equivalent  mass  of  an  atom  is  that  fraction 
of  its  mass  which  is  equivalent  to  one  atom  of  hydrogen,  the 
valence  of  an  atom,  which  is  the  ratio  of  its  atomic  mass  to 
its  equivalent  mass,  expresses  the  number  of  hydrogen-atoms 
it  can  combine  with  or  be  exchanged  for. 

EXAMTLKS. — The  valence  of  carbon  is  four,  when  one  atom  requires 
four  atoms  of  hydrogen  to  satisfy  its  chemisin.  The  valence  of  phos- 
phorus is  five,  when  it  forms  a  compound  in  which  one  atom  combines 
with  five  of  chlorine.  The  valence  of  sulphur  is  two,  when  it  can 
replace  two  atoms  of  hydrogen. 

36.  Classification  of  Atoms  according'  to  their  Va- 
lence.— Atoms  are  called  monads,  dyads,  triads,  tetrads, 
pentads,  hexads,  and  heptads  —  names  derived  from  the 
Greek  numerals — according  to  their  valence.     For  the  adjec- 
tive terms,  the  Latin  numerals  are  generally  used  ;  atoms  are 
univalent,  bivalent,  trivalent,  quadrivalent,  quinquiva- 
lent, sexivalent,  and  septivalent. 

Atoms  whose  valence  is  even,  are  sometimes  called  arti- 
ads ;  those  whose  valence  is  odd,  are  frequently  termed 
perissads. 

(A  table  of  the  valences  of  atoms  is  given  on  the  opposite 
page.) 

37.  Variation  in  Valence. — Since  one  given  element 
may  form  several  compounds  with   another  given  element, 
valence  is  evidently  not  invariable.     It  generally  increases 
or  diminishes  by  two,  however ;  so  that  an  atom  of  the  same 
element  may  in  different  compounds  have  a  valence  of  1,  3, 
5,  or  7,  or  of  2,  4,  or  6.     A  perissad  atom,  as  a  rule,  never 
becomes  an  artiad  atom  by  such  a  change,  nor  does  an  artiad 
atom  become  a  perissad. 

EXAMPLES. — Iron  in  green  vitriol  is  a  dyad,  in  pyrite  it  is  a  tetrad, 
and  in  ferric  acid  it  is  a  hexad.  Chlorine  forms  a  series  of  compounds 
with  oxygen  in  which  its  valence  is  one,  three,  five,  and  seven. 


I'AI.KXCK  OF  ATOMS. 


21 


PKKISSADS. 

A  KTIADS. 

Monads  : 

Dyad*  : 

Hydrogen 

Oxygon 

Fluorine             i,  m. 

Sulphur 
Selenium 

II,  IV,  VI. 
11,  IV,  VI. 

Chlorine             ],  in,  v,  vn. 

Tellurium 

11,   IV,  VI. 

Bromine             I,  in,  v,  vn. 
Iodine                 I,  in,  v,  vn. 

Calcium 

II,  IV. 

Strontium 

II,  IV. 

Sodium                i,  in. 

Barium 

II,  IV. 

Lithium 

Magnesium 

Potassium           i,  in,  v. 

Zinc 

Rubidium 

Cadmium 

Caesium 

Beryllium 

Silver                   I,  in. 

Mercury 

Thallium             i,  111. 

Copper 

Triad*  : 

Tetrads  : 

Nitrogen             i,  in,  v. 

Carbon 

II,  IV. 

Phosphorus        J,  in,  v. 

Silicon 

Arsenic               i,  111,  v. 

Germanium 

Antimony               in,  v. 

Titanium 

II,  IV. 

Bismuth                  in,  v. 

Tin 

II,  IV. 

Boron 

Thorium 

Gold                    i,  in. 

Zirconium 

Aluminum 
Gallium 

Platinum 
Palladium 

II,  IV. 

11,  IV. 

Indium 

Lead 

II,  IV. 

Yttrium 

Scandium 

Eexads  : 

Ytterbium 

Molybdenum 

II,  IV,  VI. 

Cerium 

Tungsten 

IV,  VI. 

Lanthanum 
Didymium 
Erbium 

Ruthenium 
Rhodium 
Iridium 

IT,  IV,  VI. 
II,  IV,  VI. 

ii,  iv,  vr. 

Pentads  : 

Osmium 

II,  IV,  VI. 

Columbium 

Chromium 

11,  IV,  VI. 

Tantalum 

Manganese 

II,  IV,  VI. 

Vanadium          in,  v. 

Iron 
Cobalt 

II,  IV,  VI. 
11,  IV. 

Nickel 

II,  IV. 

Uranium 

11,  IV,  VI. 

22  THEORETICAL  CHEMISTRY. 

Moreover,  it  would  appear  that  variability  in  valence  is 
dependent  not  only  upon  the  given  atom  itself,  but  also  upon 
the  atoms  with  which  it  combines.  In  all  hydrogen  com- 
pounds, the  valence  of  the  atom  which  is  joined  to  the  hydro- 
gen is  invariable,  only  a  single  valence  being  known  in  the 
hydrogen  compounds  of  any  given  element.  When  united 
to  chlorine,  howrever,  the  valence  is  variable,  several  chlo- 
rides being  known  of  the  same  element.  It  is,  however,  in 
oxygen  compounds  that  valence  reaches  its  greatest  variabil- 
ity, as  well  as  its  maximum  value.  Mendele'eff  has  noted 
the  fact  that  when  a  substance  forms  compounds  with  both 
hydrogen  and  oxygen,  the  sum  of  the  equivalents  of  the 
hydrogen  and  the  oxygen  in  the  highest  compounds  is  equal 
to  eight.  Thus  chlorine  forms  HC1  with  hydrogen,  and  C12O. 
with  oxygen ;  carbon  gives  CH4  and  COr  Since  oxygen  is 
bivalent,  there  is  in  the  oxygen  compound  of  chlorine  7x2 
or  fourteen  equivalents  of  oxygen  for  two  atoms  of  chlorine ; 
or  seven  equivalents  for  each.  In  the  oxygen  compound  of 
carbon,  the  oxygen  has  2x2  or  four  equivalents.  Uniting 
in  each  case  the  oxygen  equivalents  per  atom  with  the  hydro- 
gen equivalents,  we  see  that  in  the  first  case  we  have  seven 
plus  one ;  and  in  the  second  we  have  four  plus  four ;  so  that 
in  both  cases  the  sum  of  the  equivalents  is  equal  to  eight. 

The  compounds  formed  by  an  atom  with  one  valence  are 
often  widely  different  in  properties  from  those  formed  by  the 
same  element  with  a  different  valence.  Sometimes  the  iden- 
tity of  the  atom  can  be  established  only  by  the  conversion 
of  the  one  compound  into  the  other. 

EXAMPLES. — The  compounds  of  tin  in  which  this  metal  acts  with 
a  valence  of  two  are  quite  distinct  both  in  physical  and  chemical 
properties  from  the  compounds  which  contain  the  same  metal  with 
a  valence  of  four.  Lead  as  a  tetrad  forms  a  dark  brown  solid  with 
oxygen ;  while  as  a  dyad  its  compound  with  oxygen  is  an  orange- 
yellow  powder, 


THE  I'EIUOIUr  LAW.  23 

§  4.     THE  PERIODIC  LAW. 

38.  Elemental  Grouping's. — For  many  years  similarity 
of  properties  has  been  observed  between  certain  elements, 
which  has  led  to  their  being  grouped  together  in  what  are 
called  natural  families.     Moreover,  a  gradation  in  properties 
was  also  observed  in  these  groups,  which  was  easily  seen  to 
be  connected  with  a  successive  increase  in  the  atomic  mass. 

EXAMPLES. — Thus,  chlorine,  bromine,  and  iodine  have  long  been 
classed  together  as  a  natural  group,  having  similar  properties  in  gra- 
dation. Chlorine  is  a  gas,  bromine  a  liquid,  and  iodine  a  solid.  Chlo- 
rine, with  an  atomic  mass  of  35-37,  is  the  least  dense  and  the  most 
active;  while  iodine,  with  an  atomic  mass  of  1*26-54,  is  the  least  active 
and  the  most  dense.  Moreover,  the  atomic  mass  of  bromine,  the 
middle  term,  79-76,  is  very  nearly  the  mean  of  the  atomic  masses  of 
chlorine  and  iodine.  In  the  same  way  potassium,  sodium,  and  lithium 
form  a  natural  group,  having  a  similar  gradation  of  properties.  But 
in  this  case,  since  these  elements  are  electro-positive,  the  chemical 
activity,  instead  of  diminishing,  increases  with  the  atomic  mass. 

39.  Periodicity   in   Properties    of    Elements.  —  In 

1869  and  1870,  Mendeleeff  and  Lothar  Meyer  independently 
called  attention  to  the  fact  that  if  the  elements  be  arranged 
in  the  order  of  their  atomic  masses,  and  then  be  divided  into 
series  of  sevens,  placing  the  elements  of  the  second  series 
immediately  under  the  corresponding  elements  of  the  first, 
those  of  the  third  under  those  of  the  second,  and  so  on,  it 
will  be  found  that,  calling  the  elements  in  each  vertical  col- 
umn a  group,  each  of  these  groups  corresponds  to  a  natural 
family  of  elements,  having  common  properties,  varying  in 
degree  throughout  the  group.  Since  a  phenomenon  is  called 
periodic  when  it  recurs  at  definite  intervals  while  the  circum- 
stances upon  which  it  is  conditioned  vary  continuously,  it  is 
evident  that  the  properties  of  the  elements  which  recur  thus 
definitely  as  the  atomic  mass  steadily  increases  must  have 
a  periodic  dependence  upon  this  atomic  mass.  Hence  the 
law :  The  properties  of  the  elements  are  periodic  func- 
tions of  the  atomic  masses, 


24  THEORETICAL  CHEMISTRY. 

In  the  table  on  the  following  page,  the  elements  are 
arranged  substantially  according  to  Mendeleeff's  classifica- 
tion, a  horizontal  row  indicating  a  series,  and  a  vertical 
one,  a  group.  That  these  groups  constitute  natural  families 
and  contain  closely  allied  elements  appears  from  the  table 
on  page  16,  in  which  this  classification  has  been  closely  fol- 
lowed. The  elemental  properties  which  are  thus  periodic 
include  all  the  properties  of  the  elements  so  far  as  known, 
both  physical  and  chemical.  Their  hardness,  malleability, 
and  ductility  ;  their  density  and  consequent  atomic  volume  ; 
their  crystalline  form  ;  their  fusibility,  volatility,  and  specific 
heat ;  their  expansion  by  heat,  their  conductivity  for  heat, 
and  their  heat  of  combination ;  their  refractive  power  and 
the  character  of  their  spectra ;  their  electro-chemical  position, 
their  magnetic  or  diamagnetic  character,  and  their  electrical 
conductivity ;  as  well  as  their  combining  power  or  their  va- 
lence —  are  all  periodic  functions  of  their  atomic  masses. 

EXAMPLES. — Thus  the  periodicity  of  density  and  of  atomic  volume 
(which  is  the  quotient  of  the  atomic  mass  by  the  density)  appears 
clearly  in  the  third  series  of  elements  in  the  table,  as  follows : 

Na         Mg         Al  Si  P  S  Cl 

Density,  0-97        1-74        2-56        2-49        2-8          2-04         1-38 

Atomic  vol.,     23-7        13-8        10-6        11-2        13-5        15-7        25-6 

In  the  same  way,  the  refraction-equivalent  is  shown  to  be  periodic. 
Thus  in  the  second  series : 

Li          Be  B  C  N  O  F 

Eefr.  equiv_,        3-8  5-7  4-0  5-0  4-1  2-9  1-4? 

And  in  the  fourth  series : 

K          Ca  Sc          Ti  V  Cr          Mn 

Kefr.  equiv.,        8-1         10-4  ?          25-5?       25-3         15-9         12-2 

The  periodicity  of  valence  is  clearly  seen  in  the  first  and  the 
seventh  series: 

First,  Li  Be  B  C  N  O  F 

Seventh,        Ag  Ca  In  Sn  Sb  Te  I 

Valence,  1  2-3  4  3  2  1 

Graphic  construction,  however,  is  the  best  method  for  showing- 
periodicity. 


THE  PERIODIC  LA  W. 


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TREORETli  '.\L  ( 'HKMfsm  F. 


4O.  Prediction  of  Properties. — The  strongest  evidence 
of  the  truth  of  a  law  of  nature  is  its  power  to  predict.  In 
the  periodicity  table  certain  gaps  will  be  noticed  to  which  no 
known  element  belongs.  Mendeleeff  undertook  to  predict 
the  properties  of  some  of  these  undiscovered  elements,  basing 
his  predictions  on  the  periodic  law.  He  pointed  out  that,  in 
general,  the  value  of  any  property  of  an  element  is  the  mean 
of  the  values  of  the  same  property  of  the  elements  on  the 
two  sides  of  it,  whether  in  the  same  group  or  in  the  same 
series  with  it.  Thus,  for  example,  taking  the  atomic  masses, 
the  densities,  and  the  atomic  volumes  for  selenium,  we  find: 


Atomic  Musses. 


S 

31-98 

As 

Se 

Br 

74-9 

78-87 

79-76 

Te 

126-3 

Densities.                     Atomic  Volumes. 

S 

S 

2-01 

15-7 

As 

Se 

Br            As 

Se 

Br 

5-G7 

4-6 

2-97         13-2 

17-2 

2G-9 

Te 

Te 

6-25 

20-2 

To  four  elements  thus  related,  Mendeleeff  has  given  the 
name  atomic  analogues.  At  the  time  of  preparing  his 
table  gaps  existed  in  it  between  boron  and  yttrium,  between 
aluminum  and  indium,  and  between  silicon  and  tin  ;  to  which 
he  assigned  elements  having  the  provisional  names  eka-borou, 
eka-aluminum  and  eka-silicon,  respectively,  and  the  proper- 
ties of  which  he  minutely  predicted.  In  1875  Lecoq  de 
Boisbaudran  discovered  gallium,  which  proved  to  have  iden- 
tically the  properties  predicted  for  eka-alumiuum.  In  1879 
Nilson  discovered  scandium,  whose  properties  turned  out  to 
be  exactly  those  required  by  eka-boron.  And  in  1886  Wiuk- 
ler  discovered  germanium,  an  element  having  properties 
identical  with  those  which  Mendeleeff  had  assigned  to  eka- 


ATOMIC  XOTATIOX.  27 

silicon.  There  would  seem  to  be  but  little  question  there- 
fore, in  view  of  this  power  of  prediction,  that  the  periodic 
law  is  one  of  the  most  fundamental  of  all  the  laws  of  chem- 
ical science. 

§  5.     ATOMIC  NOTATION. 

41.  Atomic  Symbols. — In  1815  Berzelius  proposed  an 
abbreviated  form  of  chemical  language.     In  this  system  each 
atom  has  for  its  symbol  the  first  letter  of  its  Latin  name. 
Where  the  names  of  two  different  atoms  begin  with  the  same 
letter,  a  second  letter,  suggestive  of  the  name,  is  added. 

EXAMPLES. — O  stands  for  an  atom  of  oxygen,  I  for  one  of  iodine, 
K  for  one  of  potassium  (kalium),  Au  for  one  of  gold  (aurum),  Sn  for 
one  of  tin  (stannum).  So,  Cl  represents  an  atom  of  chlorine,  C  one 
of  carbon,  Ca  one  of  calcium,  Ce  one  of  cerium,  Cd  one  of  cadmium, 
Co  one  of  cobalt,  Cr  one  of  chromium,  Cs  one  of  caesium,  Cu  one  of 
copper  (cuprum). 

(The  symbols  of  the  elements  are  given  in  the  table  on 
page  16.) 

42.  Symbols  represent  Atomic  Masses. — Each  atomic 
symbol  stands  not  only  for  the  atom  in  general,  but  repre- 
sents particularly  its  atomic  mass. 

EXAMPLES. — Fe  (ferrum)  represents  55'88  mass-units  of  iron,  Sb 
(stibium)  1196  mass-units  of  antimony,  Hg  (hydrargyrum)  199-8 
mass-units  of  mercury,  Ag  (argentum)  107-66  mass-units  of  silver; 
these  being  the  atomic  masses  of  these  substances  respectively. 

43.  Valence  of  Atoms,  liow  Indicated. — The  valence 
of  an  atom  is  indicated  by  placing  Roman  numerals  above 
or  a  little  to  the  right  of  the  symbol.     Sometimes  minute- 
marks  are  used  instead. 

EXAMPLES. — H  or  H'  Stands  for  the  monad  hydrogen-atom ;  S  or  S" 
for  the  bivalent  sulphur-atom;  1*  or  P"'  for  the  trivalent  phosphorus- 
atom;  0,  CIV  or  C""  for  the  quadrivalent  carbon-atom;  Te  or  TeVi  for 
the  sexivalent  tellurium-atom,  etc. 


28  TffKOliETICAL  CHEMISTRY. 

44.  Graphic  Symbols.  —  The  graphic  symbol  of  an  atom 
is  a  circle,  with  lines  radiating  from  it  to  indicate  its  valence. 
These  lines  are  called  bonds.  Below  is  a  graphic  represen- 
tation of  the  seven  classes  of  atoms  : 

Monad.    'Dyad.      Triad.     Tetrad.   P^iiad.    Hexad.    Heptad. 

6  -o 


Generally,  however,  the  circles  are  omitted,  the  bonds 
radiating  from  the  symbol.  The  number  of  bonds  only  is 
significant,  not  their  direction. 

EXAMPLES.  —  Thus,  —  O  —  ,  O=,  or  O—  stands  equally  for  one  atom 
of  dyad  oxygen.  N=,  N—  ,  or  —  N=-,  equally  represents  an  atom  of 
trivalent  nitrogen. 

45.  Multiplication  of  Atoms.  —  Atoms  are  multiplied 
by  placing  an  Arabic  numeral  below  and  to  the  right  of  the 
symbol. 

EXAMPLES.  —  C.2  represents  two  atoms  of  carbon;  N4,  four  atoms  of 
nitrogen  ;  K3,  five  atoms  of  potassium  ;  Pt:t,  three  atoms  of  platinum. 

Elemental  molecules  are  represented  in  the  same  way  : 

C12  stands  for  a  molecule,  composed  of  two  atoms  of  chlorine,  O.^  for 

a  molecule  of  ozone,  As4  for  a  molecule  of  arsenic,  S6  for  a  hexatomic 

molecule  of  sulphur. 

Care  must  be  taken  not  to  confound  the  valence  marks, 
expressed  in  Roman  numerals,  with  the  number  of  atoms, 
represented  by  Arabic  numerals. 

EXAMPLES.  —  L  stands  for  three  atoms  of  iodine,  each  of  which  is 
a  monad.  Co.,  stands  for  two  atoms  of  bivalent  cobalt,  133  for  five 

IV 

atoms  of  trivalent  boron,  Si4  for  four  tetrad  silicon-atoms. 

46.  Multiplication  of  Molecules.  —  Molecules  are  mul- 
tiplied by  enclosing  their  symbols  in  brackets,  and  placing 
the  numeral  outside,  below,  and  to  the  right. 

EXAMPLES.  —  (H._,)6  stands  for  six  molecules  of  hydrogen.  (Br,J., 
represents  two  molecules  of  bromine.  (Na.2)3  indicates  three  mole- 
cules of  sodium. 


KXERCISES.  29 


EXERCISES. 


1.  Define  analysis.     Synthesis. 

2.  What   is   the   distinction  between   elementary  and  compound 
matter? 

§2. 

3.  How  do  chemists  ascertain  to  which  class  a  substance  belongs? 

4.  How  many  kinds  of  atoms  are  known? 

5.  According  to  what  rule  are  the  elements  named? 

6.  Give  Avogadro's  law  and  the  deductions  from  it. 

7.  Show  that  a  hydrogen-molecule  contains  two  atoms. 

8.  The  relative  density  of  arsenic-vapor  is  149-8;  what  is  its  molec- 
ular mass? 

9.  The  atomic  mass  of  arsenic  is  74-9;  how  many  atoms  are  there 
in  its  molecule? 

10.  The  relative  density  of  mercury  in  vapor  is  99-9;    its  atomic 
mass  is  199-8;  what  is  its  atomicity? 

11.  Mention  the  molecules  which  have  two  atomicities. 

§3. 

12.  Define  an  atom.     An  atomic  mass. 

13.  What  data  are  necessary  to  fix  an  atomic  mass? 

14.  Marsh-gas  —  a  compound  of  hydrogen  and  carbon  —  has  a  rela- 
tive density  of  8;    analysis  shows  it  to  be  composed  of  75  per  cent 
of  carbon  and  25  per  cent  of  hydrogen  ;  what  is  the  atomic  mass  of 
carbon  ? 

15.  The  analysis  of  a  compound  of  chlorine  and  antimony  gives 
40-61  per  cent  of  chlorine  and  53-39  per  cent  of  antimony;    its  rela- 
tive density  is  112-85;  what  is  the  atomic  mass  of  antimony? 

16.  How  are  positive  atoms  distinguished  from  negative? 

17.  Which  of  the  following  atoms  are  positive  and  which  negative? 
Silver  and  carbon;  tin  and  lead;  sulphur  and  chlorine;  sodium  and 
iodine. 

18.  Define  and  illustrate  valence. 


•'><)  THEORETICAL  CHEMISTRY. 

1'J.  How  are  atoms  classified  by  the  law  of'  valence? 

20.  What  is  a  dyad?     A  pentad?     A  trivalent  akmi?     A  septiva- 
lent  atom?     A  perissad?     An  artiad? 

21.  How  does  the  valence  of  an  atom  vary? 

22.  What  valence  has  oxygen  ?     Nitrogen?     Iron?     Copper? 

§4. 

23.  What  is  meant  by  a  natural  family  of  elements?     Illustrate 

24.  Define  a  periodic  property.     Why  are  the  properties  of  the  ele- 
ments called  periodic? 

25.  State  the  periodic  law.     Who  were  its  discoverers? 

26.  Illustrate  periodicity  in  the  properties  of  the  elements  from  the 
table.     How  is  a  group  of  elements  distinguished  from  a  series? 

27.  What  were  the  new  elements  whose  existence  and  properties 
were   predicted  by   Mendeleeff?      By  what  names  did   be   indicate 
them  ? 


28.  How  are  atoms  represented  in  symbols? 

29.  Give  the  symbols  of  tin,  zinc,  silver,  sodium,  aluminum. 

80.  For  what  do  the  symbols  Pb,  Ca,  K,  W,  Si,  Se,  Mn,  Mg,  stand? 

31.  How  are  two  dyad  zinc-atoms  written  ?    Four  triad  gold-atoms? 
Six  tetrad  tin-atoms?     Five  hexad  sulphur-atoms? 

32.  What  do  (fi,)G,  (#4)2,  ffi^t,  and  (§6)  represent? 


/.V.YJ/.T  MOLECULES. 


CHAPTER    THIRD. 

COMPOUND    MOLECULES. 

§  1.    BINARY  MOLECULES. 

47.  Definition. — A  compound  molecule  is  a   molecule 
whose  constituent  atoms  are  unlike. 

The  number  of  atoms  which  such  molecules  may  contain 
is  apparently  unlimited.  While  a  molecule  of  common  salt 
contains  at  least  two  atoms,  a  molecule  of  the  potassium  com- 
pound of  one  of  Dr.  Gibbs's  complex  inorganic  acids  con- 
tains 459. 

48.  Molecular  Mass. — The  molecular  mass  of  a  com- 
pound molecule,  like  that  of  a  simple  one,  is  the  sum  of  the 
atomic  masses  of  its  constituents.     It  is  always  equal  to  twice 
the  relative  density  of  the  substance  in  the  state  of  gas. 

49.  Formation   of   Molecules. — Compound  molecules 
are  formed  by  the  union  of  atoms  according  to  the  law  of 
valence. 

Since  the  number  of  bonds,  or  units  of  attraction,  is  never 
less  than  two — one  being  furnished  by  every  atom  to  each  of 
the  others  to  which  it  is  directly  united — the  entire  number 
of  bonds  in  any  molecule  must  always  be  even.  And  since, 
too,  every  perissad  atom  furnishes  an  odd  number  of  bonds, 
it  follows  necessarily,  that  the  number  of  such  atoms  con- 
tained in  any  molecule  under  normal  conditions  is  always 
even. 

5O  Classification  o£  Compound  Molecules.  —  Com- 
pound molecules  are  divided  into  two  classes : 

1st.  Those  whose  atoms  are  directly  united,  called  Bi- 
naries. 


32  THEORETICAL  CHEMISTRY. 

2d.  Those  whose  atoms  are  indirectly  united,  called  Ter- 
naries. 

51.  Binary   Molecules.  —  Binary   molecules   are    those 
whose  atoms  are  directly   united.     Whatever  the  absolute 
number  of  atoms  present  in  such  a  molecule,  they  can  never 
be  of  more  than  two  kinds. 

EXAMPLES. — A  molecule  of  salt  contains  but  a  single  atom  each  of 
chlorine  and  of  sodium ;  a  molecule  of  red-lead  consists  of  seven 
atoms,  three  of  which  are  lead-atoms,  and  four  oxygen -atoms. 

52.  Naming  of  Binary  Molecules. — The  names  of  all 
compound  molecules  are  derived  from  those  of  their  constitu- 
ent atoms;  a  plan  proposed  by  Lavoisier,  in  1787. 

A  binary  compound  is  formed  by  the  union  of  two  simple 
substances,  one  of  which,  by  the  table,  must  be  positive  to 
the  other,  which  is  negative.  Binary  molecules  are  named  : 

By  placing-  the  name  of  the  positive  constituent  first, 
and  then  the  name  of  the  negative,  the  termination  of 
which  is  changed  to  ide. 

EXAMPLES. 

Sodium  and  Chlorine      yield  Sodium  chloride. 

Magnesium  and  Oxygen  "  Magnesium  oxide. 

Silver  and  Sulphur  "  Silver  sulphide. 

Zinc  and  Phosphorus  "  Zinc  phosphide. 

Calcium  and  Iodine  "  Calcium  iodide. 

Aluminum  and  Bromine  "  Aluminum  bromide. 

Potassium  and  Nitrogen  "  Potassium  nitride. 

Barium  and  Fluorine  "  Barium  fluoride. 

Cad  mi  am,  and  Selenium  "  Cadmium  selenide, 

The  termination  IDE  is  always  characteristic  of  a  binary 
compound. 

53.  Modification  of   this   Rule. — Whenever  the  pos- 
itive  atom   enters   into   combination    with    more    than    one 
valence,  this  fact  is  indicated  in  the  compound  by  changing 
the  termination  of  the  name  of  this  atom  into  ic  or  ous. 


OF  BINARY  MOLECULES.  33 

If  the  positive  substance  acts  with  but  two  valences,  then 
in  the  higher  one  its  name  takes  the  termination  ic,  and  in 
the  lower  one  the  termination  ous. 

EXAMPLES. 

Bivalent  Mercury  and  Oxygen  form  Mercuric  oxide. 
Univalent  Mercury     "     Oxygen       "     Mercurous  oxide. 
Quadrivalent  Tin         "     Chlorine     "     Stannic  chloride. 
Bivalent  Tin  "     Chlorine     "     Stannous  chloride. 

Trivalent  Gold  "     Iodine        "     Auric  iodide. 

Univalent  Gold  "     Iodine        "    Aurous  iodide. 

If  the  positive  constituent  acts  with  more  than  two  va- 
lences the  termination  ic — being  given  on  the  discovery  of 
the  compound — is  generally  arbitrarily  assigned.  The  prin- 
cipal groups  whose  valences  thus  change,  with  the  valence  in 
the  ic  compound,  are  the  following  : 


CHLORINE   GROUP. 

SULPHUR   GROUP. 

NITROGEN    GROUP. 

Valence  F. 

Valence   VI. 

Valence  V. 

Chlorine 
Bromine 
Iodine 

Sulphur 
Selenium 
Tellurium 

Nitrogen 
Phosphorus 
Arsenic 

A  compound  in  which  the  valence  of  the  positive  is  less 
than  in  the  ous,  takes  the  prefix  hypo,  which  means  "under." 
When  this  valence  is  above  the  ic,  the  prefix  per  is  given  to 
the  name  of  the  positive.  The  negative  termination,  how- 
ever, in  all  these  cases  continues  to  be  ide. 

EXAMPLES. 

Septivalent  Chlorine        and  Oxygen  form  Per-chloric  oxide. 
Quinquivalent  Chlorine     "•    Oxygen      "     Chloric  oxide. 
Trivalent  Chlorine  "     Oxygen      "     Chlorous  oxide. 

Univalent  Chlorine  "     Oxygen      "     Hypo-chlorous  oxide. 

Sexivalent  Sulphur  "     Oxygen      "     Sulphuric  oxide. 

Quadrivalent  Sulphur        "     Oxygen      "     Sulphurous  oxide. 
Bivalent  Sulphur  "     Oxygen      "     Hypo-sulphurous  oxide. 


34  THE(tKET1f'AL  CHEMISTRY. 

Quinquivalent  Nitrogen  and  Oxygen  form  Nitric  oxide. 
Trivalent  Nitrogen  ••     Oxygen      "     Nitrous  oxide. 

Univalent  Nitrogen  "     Oxygen      "     Hypo-nitrous  oxide. 

54.  Use   of    Numeral  Prefixes.  —  In  some   cases  the 
number  of  atoms  of  each  constituent  is  to  be  indicated.    This 
is  done  by  prefixing  Greek  numerals  to  each  of  the  names 

given. 

EXAMPLES. 

1  atom    of  C  and  2  of  O  form  Carbon  di-oxide. 

1  "        of  P    "     5  of  Br  "       Phosphorus  penta-bromide. 

2  atoms  of  Fe  "     3  of  O     "       Di-1'errie  tri-oxide. 

3  "        of  Ti   "     4  of  N    "       Tri-titanic  tetra-nitride. 

55.  Notation  of  Binary  Compounds.     Formulas. — 

Notation  is  the  representation  of  a  substance  in  symbols.  If 
the  substance  be  a  compound  one,  this  representation  is  called 
a  formula. 

Binary  molecules  are  represented  by  placing  the  symbols 
of  the  constituent  atoms  together,  the  positive  first. 

EXAMPLES. 

A  molecule  of  Hydrogen  chloride  is  HC1. 
"          "          "   Cupric  oxide  "  CuO. 

"  "  Silver  iodide  "   Agl. 

"  "  "   Zinc  sulphide  "   ZnS. 

56.  Use  of  Numerals  in  Formulas. — When  the  num- 
ber of  atoms  of  any  constituent  in  a  molecule  is  more  than 
one,  this  is  indicated  by  a  numeral  placed  below  and  at  the 
right  of  its  symbol.     Compound  molecules,  like  simple  ones, 
are  multiplied  by  enclosing  them  in  brackets,  and  placing 
the  numeral  outside  and  to  the  right. 

EXAMPLES. 

SO.,     represents  1  molecule  of  Sulphuric  oxide. 
S(>2  "    Sulphurous  oxide. 

SO  "         "          "    Hypo-sulphurous  oxide. 

H.jO  "  "         "          "    Hydrogen  oxide  (water). 

Pb-jO^        "  "         "          "    Tri-plumbic  tetr-oxide, 


NOTA  WOK  OF  BINARY  MOLECULES.  35 

(Nad).,  represents  2  molecules  of  Sodium  chloride. 
(CS.2).2  2         "  "    Carbon  di-sulphide, 

(l^^o).?  3         "  "    Phosphoric  oxide. 

(As.,S3)4         "  4         "  "    Arsenous  sulphide. 

(Pb().2)  "  1  molecule    "    Lead  di-oxide. 

(PbO)2        .  "  2  molecules  "    Lead  oxide. 

57.  Formation  of  Binaries.  —  Binary  molecules  are 
generally  viewed  as  if  formed  by  the  direct  union  of  their 
constituent  atoms.  Two  cases  are  here  to  be  considered  : 

1st,   When  the  valence  of  the  atoms  is  the  same. 

2d.    When  the  valence  is  different. 

In  all  cases  of  chemical  combination,  the  chemism  of  each 
atom  must  be  satisfied.  Atoms  having  the  same  valence,  then, 
may  mutually  saturate  each  other.  Such  atoms,  therefore, 
unite  in  the  ratio  of  one  to  one. 

EXAMPLES. 

K'    and  Cl',  both  monads,  form  K'Cl',  or  K—  Cl. 

Ca"    «    O",       -     dyads,        «      Ca"O",  "  Ca=O. 

B//>     «    N///t      u     triads>        u      B"'N"',  "   B^N. 

ptiv     «    gjiv,       «     tetrads,      "      Pt'vSi'v,  "   Pt=Si. 


When  the  atoms  which  enter  into  combination  have  a  dif- 
ferent valence,  then  each  atom  must  furnish  the  same  num- 
ber of  bonds.  This  number  is,  in  all  cases,  the  least  common 
multiple  of  the  two  valences.  The  absolute  number  of  atoms 
of  each  constituent  is  obtained  by  dividing  this  least  common 
multiple  by  the  valence  of  each. 

EXAMPLES.  —  When  triad-  and  dyad-atoms  combine,  each  must  fur- 
nish six  bonds  —  the  least  common  multiple  of  3  and  2.  But  to  furnish 
six  bonds,  three  dyad-atoms  and  two  triad-atoms  are  required.  Hence 
the  molecule  will  consist  of  two  atoms  of  the  triad  and  three  of  the 
dyad. 

So  a  tetrad  uniting  with  a  dyad  will  require  four  bonds  —  the  least 
common  multiple  of  4  and  2  —  to  furnish  which  one  tetrad-atom  and 
two  dyad-atoms  are  necessary.  The  following  formulas  still  further 
illustrate  this  law; 


36  THEORETICAL  rH 

H',  a  monad,  and  O",  a  dyad,  form  H'.2O". 
N'",  a  triad,  and  O",  a  dyad,  form  N'^O",, 
Snlv,  a  tetrad,  and  8",  a  dyad,  form  Sn'vS"2 
B'",  a  triad,  and  01',  a  monad,  form  B'^Cl^ 
Silv,  a  tetrad,  and  F',  a  monad,  form  Si'VF'4 
Biv,  a  pentad,  and  S",  a  dyad,  form  Biv.2S"5 
Pv,  a  pentad,  and  Br',  a  monad,  form  P^Br'.- 
S«,  a  hexad,  and  O",  a  dyad,  form  SVIO", 
Clvl1,  a  heptad,  and  O"  a  dyad,  form  C1VII.,O"7 

Where  perissad-  and  artiad-atoms  form  a  molecule,  the 
number  of  atoms  required  is  inversely  as  the  valence  of 
each. 

This  rule  requires  to  be  modified,  however,  in  cases  when; 
atoms  of  the  same  polyad  element  unite  with  each  other 
directly;  a  condition  of  things  appearing  markedly  in  the 
case  of  carbon.  While  one  atom  of  carbon  unites  with  four 
of  hydrogen,  two  atoms  of  carbon  unite  not  with  eight,  but 
with  six  hydrogen-atoms ;  two  of  the  bonds  of  the  two  car- 
bon-atoms being  occupied  in  holding  these  atoms  together ; 
thus 

H    H 

H— C— C— H 

U 

Consequently  the  maximum  number  of  monad  atoms  with 
which  n  carbon-atoms  can  combine  is  not  4n,  but  2n-f  2. 
Hence  the  homologous  series  CH4,  C2H6,  C3HH,  C4H10,  C5H12, 
C6H14,  etc.,  the  members  of  which  differ  from  those^preceding 
or  following  them  by  CH2. 

58.  Exchange  of  Atoms  in  forming*  Binaries. — As 
atoms  do  not  exist  free,  they  can  not  in  fact  form  molecules 
by  directly  combining.  Binary  compound  molecules  are 
formed  from  the  elemental  molecules  of  their  constituents, 
which,  being  brought  into  proximity,  have  their  .atoms  re- 
arranged ;  the  intensity  of  the  chemical  attraction  between 


A  TriiA  TED  MOLEC  UL  KS.  37 


two  dissimilar  atoms  being  stronger  than  that  exerted  be- 
tween two  similar  atoms. 

EXAMPLES.  —  A  molecule  of  magnesium  Mg  —  Mg,  when  brought 
in  contact  with  one  of  oxygen  O=^O,  under  suitable  conditions  will 
exchange  one  of  its  magnesium-atorns  for  an  atom  of  oxygen  to  form 
two  molecules  of  magnesium  oxide  Mg  =  O,  O  =Mg.  It  may  be  rep- 
resented thus: 

Mg  O  Mg  =  0 

Before    ||  j|  After 

Mg  O  Mg  =  O 

In  the  same  way  two  molecules  of  hydrogen  and  one  of  oxygen 
wiil  form  two  molecules  of  hydrogen  oxide  or  water,  thus: 

H        O        H  II  —  O  —  H 

Before    |  ||  |  After 

H        O        II  H  —  O—  H 

59.  Uiisaturated  Molecules.     Compound  Radicals. 

Besides  the  atomic  groups  now  considered,  called  saturated 
molecules  because  the  bonds  of  all  the  atoms  they  contain 
are  mutually  engaged,  it  is  often  convenient  to  distinguish 
certain  unsaturated  groups  of  atoms,  which,  possessing  free 
bonds,  may  enter  into  combination  like  single  atoms.  These 
uusaturated  groups  of  atoms  are  frequently  called  com- 
pound radicals.  They  can  not  exist  in  a  free  state  in 
nature,  though,  like  an  atom,  by  combining  with  another 
similar  group,  they  may  form  a  molecule  which  is  saturated. 
Their  valence  is  always  equal  to  the  number  of  unsatisfied 
bonds  ;  i.  e.,  is  the  difference  of  the  valences  of  their  constit- 
uents. 

EXAMPLES.  —  "Water  is  H  —  O  —  H;  by  removing  one  hydrogen- 
atom,  there  is  left  the  unsaturated  group  H  —  O  —  ,  which,  though 
consisting  of  two  atoms,  is  capable  of  entering  into  the  formation  of 
a  molecule  like  any  single  atom.  It  has  one  free  bond,  and  hence 
acts  as  a  monad.  But  by  combining  with  another  similar  group,  it 
forms  H  —  O  —  O  —  H,  a  free  saturated  molecule.  This  compound 
radical  may  also  be  written  (H'O")'. 

So  H.{N,  a  saturated  molecule  of  ammonia,  yields  (H2N)',  a  monad 

compound  radical,  by  the  loss  of  H'.     I*  a  pentad  phosphorus-atom, 

4 


38  THEORETICAL   CHEMISTRY 

may  be  partially  saturated  by  one  oxygen-atom  O",  forming  the  triva- 
lent  compound  radical  (P'O")'";  or  by  two  oxygen-atoms,  gi  /ing  the 
univalent  radical  (P'O2")'.  The  former  (PO)'"'  may  unite  with  Cl 
like  any  other  triad,  forming  (PO)"'C13. 

60.  Names  of  Compound  Radicals. — Compound  rad- 
icals have  names  terminating  in  yl.     The  root  of  the  name 
comes  either  from  their  constituents  or  from  some  compound 
into  which  they  enter. 

EXAMPLES. — The  compound  radical  (HO/  is  called  hydroxyl; 
(PO)'"  is  named  phosphoryl ;  (CO)"  carbonyl,  (CH3)'  methyl,  from 
methyl  alcohol,  of  which  it  is  a  constituent.  Three  compound  rad- 
icals, (H2N)'  amidogen,  (CN)'  cyanogen,  and  (H4NV)'  ammonium,  are 
exceptions  to  this  rule. 

61.  Artiad  and  Perissad  Radicals. — Perissad  radicals, 
having  an  uneven  number  of  free  bonds,  can  exist  free  only 
by  combining  with  each  other,  as  above  stated.     Artiad  rad- 
icals, having  an  even  number  of  free  bonds,  may  exist  in  the 
free  state  by  the  mutual  saturation  of  these  bonds  by  each 
other. 

EXAMPLES. — Nitryl  (NO2)',  a  perissad  radical,  can  not  exist  free. 
But  by  combining  with  another  group,  (NO2) —  (NO2)  is  produced, 

H     H 

which    is    saturated.       Ethylene,    H  — 0  — C  — H   or    (C.,H4)"    is    a 

I        I 

bivalent  radical;    but   by   doubly  uniting   the   carbon,    oleliant   gas 
H      H 

H — C  =  C —  H  results.  Carbonyl  O=:C  —  is  a  dyad  radical, 
O  =  C>  is  free  carbon  monoxide. 

62.  Explanation  of  Variation  in  Atomic  Valence. 

By  a  similar  hypothesis  some  chemists  have  attempted  to 
explain  the  variation  in  atomic  valence.  An  atom  is  assumed 
to  have  but  one  valence,  which  is  the  highest  it  ever  exhibits. 
If  now  two  of  its  bonds  mutually  saturate  each  other,  the 
atom  has  a  less  valence  by  two ;  if  two  pairs  thus  saturate, 


TKll  AV/  /,'  I  "  MOL  EC  ULES.  39 

by  four  ;  if  three,  by  six.  A  heptad  may  thus  become  a 
pentad,  triad,  and  monad  successively  ;  and  a  hexad  may  be- 
come a  tetrad,  and  a  dyad  ;  as  the  following  graphic  formu- 
las show  : 

Pentad.  Triad.  Monad. 


Hexad.  Tetrad.  Dyad. 


^ 

In  the  case  of  those  elements  which,  like  mercury,  copper, 
iron,  vanadium,  etc.,  appear  to  act  with  an  even  valence  in 
some  of  their  compounds  and  with  an  odd  valence  in  others, 
we  can  only  accept  the  fact  and  write  the  formulas  in  the 
simplest  way  ;  awaiting  new  light  upon  the  nature  of  valence 
itself,  in  order  to  explain  the  anomaly. 

63.  Names  of  Molecules  formed  by  Radicals.  — 
Molecules  which  contain  compound  radicals  united  to  ele- 
mentary atoms  are  classed  as  binaries  and  are  named  in  the 
same  way. 

EXAMPLES.  —  Nitryl  (NO2)y  and  chlorine  form  nitryl  chloride 
(NO2)'C1.  Carbonyl  (CO)"  and  sulphur  form  earbonyl  sulphide 
(CO)"S.  Methyl  (CH,)'  and  oxygen  form  (CH3)'2O,  methyl  oxide. 


§  2.     TERNARY  MOLECULES  UNITED  BY  DYADS. 

64.  Classification  of  Ternary  Molecules. — Ternary 
molecules  are  those  whose  dissimilar  atoms  are  united  by  the 
aid  of  some  third  atom.  This  third  atom,  which  performs  a 
linking  function,  must  evidently  be  a  polyad,  since  no  monad 
can  join  other  atoms  together. 

Ternary  molecules  are  divided  into  two  classes  according 
to  the  valence  of  the  uniting  atom : 


40  THEORETICAL  CHEMISTRY. 

1st.   Ternary  molecules  united  by  bivalent  atoms. 
2d.    Ternary  molecules  united  by  trivalent  atoms. 

65.  Ternary  Molecules  united  by  Dyads. — The  dyads 
oxygen,   sulphur,   selenium,  and  tellurium,  may  perform  a 
linking  function.     Of  the  compounds  thus  formed,  by  far 
the  larger  proportion  are  compounds  of  oxygen.     Oxygen, 
therefore,  is  the  distinguishing  component  of  this  class  of 
bodies. 

66.  Ternary   Molecules   linked   by   Oxygen. — Oxy- 
gen, by  its  two  bonds,  may  unite  two  atoms  or  groups  of 
atoms  together.      Bodies  thus  constituted  are  divided  into 
three  classes,  according  to  the  character  of  the  atoms  which 
are  thus  united.     These  classes  are  called  acids,  bases,  or 
salts. 

67.  Definition  of  an  Acid. — An  acid  molecule  is  one 
which  consists  of  one  or  more  negatiye  atoms  united  by 
oxygen  to  hydrogen. 

The  general  formula  of  an  acid,  therefore,  is  R  —  O  —  H. 
The  number  of  hydrogen-atoms  which  it  contains  is  equal  to 
the  valence  of  the  negative  atom  or  group  of  atoms.  In 
general,  acids  are  recognized  by  the  property  which  they 
possess  of  turning  certain  vegetable  blues  to  red. 

68.  Definition  of  a  Base. — A  basic  molecule  consists 
of  one  or  more  positive  atoms  united  by  oxygen  to  hy- 
drogen. 

A  base  is  the  analogue  of  an  acid.     It  has  the  general 

formula  R —  O  —  H,  the  number  of  hydrogen  -  atoms  de- 
pending, as  before,  upon  the  valence  of  the  positive  atom  or 
atomic  group.  Bases  restore  the  color  to  vegetable  blues 
which  have  been  reddened  by  an  acid. 

69.  Definition  of  a  Salt. — A  saline  molecule  is  one 
which  contains  a  positive  atom  or  group  of  atoms  united 
by  oxygen  to  a  negative  atom  or  group  of  atoms. 

The  general  formula  of  a  salt  is  R  —  0  —  R,     As  it  con- 


TERNARY  MOLECULES.  41 

tains  no  hydrogen  it  has  neither  acid  nor  basic  properties, 
and  is  therefore  without  action  upon  vegetable  colors. 

70.  Water  Type. — A  molecule  of  water  consists  of  two 
atoms  of  hydrogen  linked  together  by  oxygen,  thus:  H  —  O 

—  H.  By  exchanging  one  of  these  hydrogen-atoms  for  a 
negative  monad,  an  acid,  R —  O  —  H,  is  produced.  By  a 
similar  exchange  for  a  positive  atom,  a  base,  R  —  O  —  H,  is 
obtained.  By  replacing  both  of  the  hydrogen-atoms,  one  by 
a  positive  the  other  by  a  negative  atom,  a  salt,  R  —  O  —  R, 
results.  Hence  these  three  classes  of  bodies  are  sometimes 
said  to  be  formed  upon  the  plan  of  structure  of  water ;  that 
is,  upon  the  water  type. 

Acids  and  bases  may  also  be  viewed  as  compounds  of  the 
monad  radical  hydroxyl.  If  hydroxyl  H — O —  unite  with 

R,  it  forms  an  acid  R— O— H;  if  with  R,  it  gives  a  base  R— 
O — H.  This  method  of  viewing  acids  and  bases  is  conven- 
ient for  many  purposes. 

71.  Naming-  of  Acids,  Bases,  and  Salts. — Acids,  bases, 
and  salts,  like  binaries,  are  named  from  their  constituent 
atoms.     The  termination  of  the  negative  is  changed,  how- 
ever, to  indicate  that  the  atoms  are  linked  by  oxygen.    These 
negative  ternary  terminations  are  universally  ate  and  ite. 

EXAMPLES.  —  Potassium  and  sulphur  when  directly  united,  form 
potassium  sulphide;  when  united  by  oxygen,  potassium  sulphate,  sul- 
phite, or  hypo-sulphite,  according  to  the  valence  of  the  sulphur.  The 
binary  hydrogen  nitride  becomes,  by  the  introduction  of  linking  oxy- 
gen, hydrogen  nitrate  or  nitrite,  both  ternary  acids.  And  in  the  same 
way,  copper  hydride  becomes  copper  hydrate. 

The  name  hydroxide  is  sometimes  used  to  indicate  a  more 
intimate  union  or  a  chemical  union  proper  ;  the  word  hydrate 
being  employed  to  signify  a  less  intimate  physical  or  molec- 
ular union.  Thus,  if  sodium  oxide  unites  with  hydrogen 
oxide,  sodium  hydroxide  results ;  while  if  sodium  carbonate 
so  unites,  a  hydrate  of  sodium  carbonate  is  the  product. 


42  THEORETICAL  CHEMISTRY. 

72.  Change  in  Termination  of  the  Positive  Atom. 

The  positive  atom,  as  in  binaries,  retains  its  name  unaltered 
except  when  it  acts  with  more  than  one  valence.  It  then 
takes  the  termination  ous  and  ic. 

EXAMPLES. — Mercurous  and  mercuric  nitrates,  cuprous  and  cuprio 
sulphates;  ferrous  and  ferric  phosphates,  stannous  and  stannic  sili- 
cates, etc. 

73.  Common  Names  of  Acids  and  Bases. — As  both 
acids  and  bases  contain  oxygen  and  hydrogen,  they  are  com- 
monly named  from  the  characteristic  constituent,  giving  it 
the  termination  ic  or  ous,  according  to  its  valence,  and  add- 
ing the  word  acid  or  base. 

EXAMPLES. — The  common  name  of  hydrogen  sulphate  is  sulphu- 
ric acid;  of  hydrogen  nitrite,  nitrous  acid;  of  hydrogen  phosphate, 
phosphoric  acid;  of  hydrogen  hypo-chlorite,  hypo-chlorous  acid.  So 
too,  calcium  hydrate  is  calcic  base;  zinc  hydrate,  zincic  base;  ferric 
hydrate,  ferric  base;  ferrous  hydrate,  ferrous  base;  aluminic  hydrate, 
aluminic  base. 

74.  Formation  of  Ternary  Molecules. — Ternary  mole- 
cules are  formed  in  two  ways: 

1st.  By  the  direct  union  of  binary  molecules. 
2d.  By  substitution,  from  each  other. 

75.  Formation  of  Ternaries  hy  Direct  Union. — Ter- 
naries are  formed  by  the  direct  union  of  the  oxide  of  a  more 
positive  atom  with  the  oxide  of  a  less  positive  or  negative 
one.     In  this  case,  the  name  oxide  is  dropped,  and  the  name 
of  the  negative  takes  ate  if  it  terminated  before  an  ic ;  or 
ite  if  it  ended  before  in  ous.     Whenever  water  is  the  nega- 
tive oxide,  the  body  produced  is  a  base ;  when  it  is  the  posi- 
tive, the  ternary  is  an  acid. 

EXAMPLES.  —  Sodium  oxide  and  phosphoric  oxide  unite  to  form 
sodium  phosphate;  here  the  "oxide"  of  both  is  dropped,  and  the  ic  of 
the  negative  oxide  is  changed  into  ate.  So  calcium  oxide  and  sulphu- 
rous oxide  form  calcium  sulphite.  Silver  oxide  and  hypo-chlorous 
oxide  form  silver  hypo-chlorite.  Again,  when  hydrogen  oxide — wa- 
ter—  unites  with  sulphuric  oxide,  hydrogen  sulphate,  or  sulphuric 


TERNARY  MOLECULES.  43 

acid,  results;  when  it  unites  with  potassium  oxide,  potassium  hydrate 
(or  hydroxide)  is  produced,  the  water  being  now  negative. 

Negative  oxides  are  sometimes  called  anhydrides,  because 
they  may  be  formed  from  acids  by  the  abstraction  of  water. 

76.  Formation  of  Ternaries  by  Substitution. — Ter- 
naries are  also  formed  from  each  other,  by  substitution.     An 
acid,  by  exchanging  its  hydrogen  for  a  positive  atom,  becomes 
a  salt ;  a  base,  exchanging  its  hydrogen  for  a  more  negative 
substance,  becomes  also  a  salt ;  a  salt  may  become  an  acid  or 
a  base,  according  as  its  positive  or  its  negative  constituent  is 
replaced  by  hydrogen  ;  and  by  exchanging  positive  for  nega- 
tive atoms,  or  the  reverse,  bases  may  be  converted  into  acids 
or  acids  into  bases. 

EXAMPLES. — Hydrogen  chlorate  or  chloric  acid,  by  exchanging  its 
hydrogen  for  barium,  becomes  barium  chlorate,  a  salt.  Lithium  hy- 
drate, or  lithic  base,  by  exchanging  its  hydrogen  for  carbon,  becomes 
lithium  carbonate,  also  a  salt.  So  magnesium  silicate  becomes  hydro- 
gen silicate  or  silicic  acid,  by  replacing  its  positive  portion  by  hydro- 
gen, and  magnesium  hydrate  or  magnesic  base,  by  replacing  its  nega- 
tive portion  "by  the  same  element. 

Whenever  a  base  and  an  acid  are  brought  in  contact,  a 
salt  and  water  are  produced.  Or,  graphically,  R— O— H 
and  R-O-H  produce  R-O-R  and  H-O-H. 

77.  Classification  of  Acids.  —  Acids  are  divided  into 
two  classes,  called  normal  or  ortho-acids  and  meta-acids. 

1st.  Ortho-acids  are  those  acids  in  which  all  the  oxygen 
has  a  linking  function.  In  these  acids,  therefore,  there  are 
as  many  atoms  of  hydrogen  and  of  oxygen  —  i.  e.,  of  hy- 
droxyl — as  is  equal  to  the  valence  of  the  negative  atom  rr 
atomic  group. 

EXAMPLES. 

Clvi'(OH)7  is  ortho-perchloric  acid. 
C1V(OH)5  is  ortho-chloric  acid. 
C1'"(OH)3  is  ortho-chlorous  acid. 
Cr(OH)  is  ortho-hypo-chlorous  acid. 


44  THEORETICAL  CHEMISTRY. 

SVI(OH)6  is  ortho-sulphuric  acid. 
SIV(OH)4  is  ortho-sulphurous  acid. 
S''(OH)2  is  ortho-hypo-sulphurous  acid. 

2d.  Meta-acids  are  acids  which  contain  saturating  as  well 
as  linking  oxygen.  The  oxygen  atoms  therefore,  in  a  meta- 
acid,  always  exceed  the  hydrogen  atoms. 

EXAMPLES. 

(CIO)'(OH)  is  meta-chlorous  acid  or  hydrogen  metn-chlorite. 
(CO)"(OH).2  is  meta-carhonic  acid  or  hydrogen  mete-carbonate. 
(PO)"'(OH)3  is  meta-phosphoric  acid  or  hydrogen  meta-phosphate. 
(CrO)'v(OH)4  is  mete-chromic  acid  or  hydrogen  meta-chromate. 
(IO)V(OH)5  is  meta-pcr-iodic  acid  or  hydrogen  meta-per-iodate. 

78.  Formation  of  Meta-acids. — Meta-acids  are  derived 
from  ortho-acids  by  subtracting  from  them  one  or  more  mole- 
cules of  water ;  the  acid  being  mono-,  di-,  or  tri-meta,  accord- 
ing to  the  number  of  molecules  of  water  taken  from  the 
ortho-acid  to  form  it. 

EXAMPLES. 

Svi(OH)6,  less  H2O,  leaves  (SO)'V(OH)4,  mono-meta-sulphuric  acid. 
SVI(OH)6,  less  (H2O)2,  leaves  (SO2)"(OH).,,  di-nieta-suiphuric  acid. 
NV(OH)3,  less  H2O,  leaves  (NO)'"(OH).5,  mono-meta-nitric  acid. 
NV(OH)5,  less  (H2O)2,  leaves  (NO2)/(OH),  di-meta-nitric  acid. 
As'"(OH),,,  less  H2O,  leaves  (AsO)'(OH),  mono-meta-arsenous  acid. 

The  precise  manner  in  which  the  molecule  is  affected  by 
this  abstraction  of  water  is  represented  by  the  following 
graphic  formulas  showing  the  production  of  the  meta-per- 
chloric  acids : 

OrtJto-  Mono-meta-          Di-mela-  Tri-meia- 

perchloric.          perchloric.         perchloric.        perchloric. 


0^cz^0         ^a^       ^0-^1=0     o=a=o 

$    Q,  o  ^    o  o 

Every  molecule  of  water  thus  removed,  it  should  be  ob- 


TERNARY  MOLECULES.  45 

served,  leaves  one  atom  of  saturating  oxygen.  Hence  every 
mono-meta-acid  has  one  such  atom,  every  di-meta-acid  two, 
and  every  tri-meta-acid  three. 

TABULAR  VIEW  OF  ORTHO-  AND  META-ACIDS. 

Monads   Dyads      Triads     Tetrads   Pentads   Hexads  Heptads 

Mono-meta  HKO,    H.AiO,  H,fiO4  H4^O.  H-ViiO,. 

•<5  &  o  .1  4          4  D          o  f» 

Di-meta  Hlk)3    HjlO4  H3VJk>5 

Tri-meta  HKO4 

79.  Basicity  of  Acids. — The  hydrogen  in  an  acid  which 
is  linked  to  the   atomic   group  by  oxygen  is  called  basic 
hydrogen  because  it  is  readily  exchanged  for  a  more  posi- 
tive atom  or  group  of  atoms.     Acids  are  said  to  be  mono- 
basic, di-basic,  tri-basic,  or  tetra-basic,  according  as  they  con- 
tain one,  two,  three,  or  four  atoms  of  basic  hydrogen.     All 
acids  are  poly-basic   which   contain  within   their  molecules 
more  than  one  of  these  hydroxyl  groups. 

EXAMPLES. 

(NO.,)'(OH),  di-meta-nitric  acid,  is  monobasic. 
(CO)"(OH)2,  mono-meta-carbonic  acid,  is  dibasic. 
B///(OH)3,  ortho-boric  acid,  is  tribasic. 

In  all  ortho-acids  the  basicity  is,  of  course,  equal  to  the 
valence  of  the  negative  atom. 

80.  Ortlio-  and  Meta-bases. — Like  acids,  bases  may  be 
either  ortho-  or  meta-,  and  for  the  same  reasons.     But,  since 
positive  atoms  rarely  vary  in  valence,  but  a  very  few  meta- 
bases  are  known. 

EXAMPLES. 

K'(OH)  is  ortho-potassic  base,  or  ortho-potassium  hydrate. 
Ca"(OH).,  is  ortho-calcic  base,  or  ortho-calcium  hydrate. 
Ptlv(OH)4  is  ortho-platinic  base,  or  ortho-pi atinic  hydrate. 
Fe.2vl(OH)H  is  ortho-ferric  base,  or  ortho-ferric  hydrate. 
ZrO(OH).2  is  meta-zirconic  base,  or  meta-zirconium  hydrate. 
Fe2viOa(OH)2  is  di-meta-ferric  base,  or  di-meta-ferric  hydrate. 


46  THEORETICAL  CHEMISTRY. 

81.  Acidity  of  Bases. — The  hydrogen  of  a  base  is  called 
acid  hydrogen,  because  it  is  replaceable  by  a  negative  atom. 
The  acidity  of  a  base  depends  upon  the  number  of  hydroxyl 
groups,  like  the  basicity  of  an  acid.     Bases  are  mon-acid,  di- 
acid,  tri-acid,  etc.,  as  acids  are  mono-basic,  etc. 

EXAMPLES. 

Argentic  base  Ag'(OH)  is  mon-acid. 
Ferrous  base  Fe"(OH).,  is  di-acid. 
Aluminic  base  A1'"(OH)3  is  tri-acid. 

82.  Formation  of  Stilts. — Salts  are  formed  from  acids 
by  replacing  their  basic  hydrogen  by  positive  atoms. 

If  the  acid  has  its  systematic  name,  the  name  of  the  salt 
is  obtained  from  it  by  putting  the  name  of  the  positive  atom 
in  place  of  the  hydrogen. 

If  the  acid  has  its  common  name,  the  name  of  the  salt  is 
formed  by  placing  the  name  of  the  positive  atom  first,  fol- 
lowed by  that  of  the  acid,  the  termination  ic  being  changed 

to  ate,  and  cms  to  ite. 

EXAMPLES. 

Hydrogen  nitrate,  or  nitric  acid,  and  sodium,  give  sodium  nitrate. 

Hydrogen  chlorite,  or  Chlorous  acid,  and  barium,  give  barium  chlo- 
rite. 

Hydrogen  bypo-iodite,  or  bypo-iodous  acid,  and  zinc,  give  zinc 
hypo-iodite. 

83.  Formulas  of  Salts. — In  writing  the  formula  of  a 
salt,  regard  must  be  had  both  to  the  basicity  of  the  acid 
and  to  the  valence  of  the  replacing  atom.     As  many  mole- 
cules of  the  acid  must  be  taken  as  is  necessary  to  furnish  a 
number  of  hydrogen-atoms  equal  to  the  least  common  mul- 
tiple of  the  basicity  of  the  acid  and  the  valence  of  the  re- 
placing atom. 

EXAMPLES. — It  is  required  to  write  the  formula  of  calcium  phos- 
phate. Calcium  phosphate  is  derived  from  hydrogen  phosphate — 
phosphoric  acid --by  replacing  hydrogen  by  calcium.  The  formula 
of  mono-meta-phosphoric  acid  —  the  most  common  form,  and  there- 
fore referred  to  when  no  other  is  specified  —  is  PO"'(0H.)8  or  more 


TERNARY  MOLECULES. 


47 


conveniently,  H;JPO4.  Calcium  is  a  dyad ;  the  acid  is  tri-basic ;  the 
least  common  multiple  of  two  and  three  is  six;  as  many  molecules 
of  the  acid  are  required  as  is  necessary  to  yield  six  hydrogen  atoms ; 
this  number  is  two,  written  (HjPO4)g,  or  for  convenience  of  replace- 
ment H6(PO4).;.  The  six  atoms  of  hydrogen  can  be  exchanged  for 


three  of  Ca";   makins 
phosphate. 


this  change,  we  have  Oa"3(PO4)2,  or  ealciiur. 


Mono-basic  Acids. 


Sodium  nitrate. 
Calcium  nitrite. 
Bismuthous  chlorate. 
Zirconium  phosphate. 

Potassium  sulphite. 
Barium  carbonate. 
Auric  chromate. 
Platinic  sulphate. 


Silver  arsenate. 
Zinc  iodate. 
Bismuthous  nitrate. 
Stannic  antimonite. 


Caesium  silicate. 
Ferrous  selenate. 
Auric  carbonate. 
Zirconium  tellurite. 


84.  Salts  derived  from  Bases. — Salts  may  be  derived 
from  bases  as  well  as  from  acids.     They  are  viewed  as  so 
derived  only  in  a  few  cases,  where  they  form  a  peculiar  class 
of  basic  salts. 

85.  Normal,  Acid,  Basic,  and  Double  Salts. — Nor- 
mal salts  are  salts  which  contain  neither  basic  nor  acid 
hydrogen.*    They  are  formed  by  the  complete  replacement 
of  the  hydrogen  of  an  acid  or  a  base. 

Acid  salts  are  those  which   contain  basic  hydrogen. 


Na' 
Ca" 
Bi'" 
Zr'v 

and  HNO3 

and  (HNO.2)2 
and  (HC1O3)3 
and  (HPO3)4 

give  Na'NO3 
"     Ca"(NO2)2 

Di-basic  Acids. 

Ba" 
'  Au'"2 

Pt'v 

and  H2SO3 
and  H.2CO:5 

and  (H,CrO4), 
and  (H~S04)2 

give  K'2SO3 
"     Ba"CO., 

Tri-basic  Adds. 

Ag'3 
Zn", 
Bi'" 

and  H3AsO4 

and  (H3IO4)2 
and  H3NO4 
and  (H,SbO3)4 

give  Ag'gAsOj 

•;«     Zn"3(I04).2 
"     Bi'"(NO4) 
"     Sniv8(Sb03)4 

Tetra-basic  Acids. 

Cs'4 
Fe"2 
Au"'4 

Zr'v 

and  H4SiC4 
and  H4SeO- 
and  (H4CO4):5 
and  H/TeCX 

give  Cs4SiO4 
"     Fe"2SeO5 
«     Au///4(C04), 
"     Zr'VTeO, 

48  THEORETICAL  CHEMISTRY. 

The  replacement  in  the  acid  being  only  partial,  the  salt  still 
acts  like  an  acid,  turning  vegetable  blues  to  reds. 

Basic  salts  are  salts  formed  by  the  partial  replace- 
ment of  the  hydrogen  of  a  base  by  a  negative  atom. 
They  contain  therefore  acid  hydrogen,  and  often  act  like  a 
base  upon  vegetable  colors. 

Double  salts  are  salts  containing  two  or  more  differ- 
ent positive  atoms. 

EXAMPLES. 

Normal  Salts.  Acid  Salts. 

Potassium  chlorate  KC103  Hydro-sodium  sulphite  HNaS03 

Calcium  sulphate  Ca"SO4  Hydro-caesium  carbonate  HCsCO.} 

Bismuthous  phosphate  Bi'"PO4  Hydro-barium  phosphate  HBaPO4 
Sodium  silicate  Na2SiO3  Hydro-cupric  silicate  H2CuSiO4 

Basic  Salts. 

Lead  hydro-nitrate  H(NO2)/PbOa 

Copper  hydro-acetate       H(Ac)/CuO2 
Mercuric  hydro-iodite      H(IO)'HgO.j 

Aluminic  hydro-silicate  H2SilvAl2OG 

Double  Salts. 

Potassio  sodium  selenate     KNaSeO4 
Sodio-caloiurn  antimonate  NaCa"SbO4 
Baro-zincic  silicate  Ba//Zn//SiO4 

Caesio-rubidic  carbonate      Cs'Rb'CO:i 

Mono-basic  acids  can  form  only  normal  salts.  Poly-basic 
acids  can  form  normal,  acid,  and  double  salts. 

86.  Empirical  and  Rational  Formulas. — An  empir- 
ical or  experimental  formula  is  one  derived  from  analysis. 
It  expresses  the  kind  and  relative  number  of  atoms  in  the 
molecule.  It  may  be  also  a  true  molecular  formula,  in 
which  case  it  expresses  the  absolute  number  of  atoms  the 
molecule  contains. 

A  rational  formula  not  only  expresses  the  kind  and  the 
absolute  number  of  atoms  contained  in  any  molecule,  but 
also  indicates  how  those  atoms  are  arranged.  All  graphic 
formulas  are  rational. 


V'AV.'.V.  I  /•'  1  '  MOL  ECULES.  49 

EXAMPLES.—  HNO3,  CaCl2O2,  HgCl,  CuClO3,  are  all  empirical  for- 
mulas, derived  from  analysis.  The  first  two  are  molecular,  and  ex- 
press the  absolute  number  of  atoms;  but  the  molecular  formulas  of 
the  second  two  are  Hg2Cl2  and  Cu2Cl2O6,  the  molecule  having  twice 
the  mass  in  each  case. 

The  rational  formulas  of  the  four  bodies  above  given,  represented 
graphically,  are: 

0  O—  01  O  O 

II  I  Hg-Cl  |!  || 

N—  OH,    Ca  and    Cl—  O—  Cu—  Cu—  O—  Cl 

II  I  Hg-Cl,  ||  || 

O  O-C1,  O  O 

The  same  substances  are  thus  represented  in  symbols: 


/MO  MW      r  T   f  CuO(CK).,) 

(N02)OH,     Ca''      and2 


\  CuO(ClO2) 

87.  Sulphur  and  Selenium  Acids,  Bases,  and  Salts. 

The  atoms  of  ternary  molecules  may  be  united  by  the  neg- 
ative dyads  sulphur  and  selenium,  as  well  as  by  oxygen. 
These  molecules  are  named  and  formulated  in  precisely  the 
same  way  as  those  formed  by  oxygen,  and  are  distinguished 
from  these  by  the  prefix  sulph-  or  selen-,  given  to  the  neg- 
ative name. 

EXAMPLES. 

As(OH)3  Hydrogen  arsenite  As(SH)3  Hydrogen  sulph-arsenite. 
Sb(OAg)3  Silver  antimonite  Sb(SAg)3  Silver  sulph-antimonite. 
SbO(ONa)3  Sod.  antimonate  SbS(SNa)3  Sod.  sulph-antimonate. 
SbO(OK)3  Potas.  antimonate  SbSe(SeK)3  Potas.  selen-antirnonate. 

The  sulphur  and  selenium  in  a  molecule  may  be  saturat- 
ing, or  linking,  or  both.  These  two  substances,  and  also 
oxygen,  may  co-exist  in  the  same  molecule. 

§  3.   TERNARY  MOLECULES  UNITED  BY  TRIADS. 

88.  Classification  of  Molecules  united  by  Nitrogen. 

The  negative  triads  which  may  perform  a  linking  function 
are  nitrogen,  phosphorus,  and  arsenic.  Of  these,  but  a  few 
compounds  united  by  phosphorus  or  arsenic,  and  these  com- 


50  THEORETICAL   CHEMISTRY. 

paratively  unimportant,  are  known.  Molecules  whose  atoms 
are  united  by  nitrogen  are  divided  into  three  classes,  on  the 
same  principle  upon  which  those  united  by  negative  dyads 
are  classified.  These  classes  are  called  amides,  amines,  arid 
alkalamides. 

89.  Definition  of  an  Amide. — An  amide  is  made  up 
of  molecules  consisting  of  one  or  more  negative  atoms  united 
by  nitrogen  to  hydrogen. 

The  general  formula  of  an  amide  is  R — N=H.2. 

90.  Definition  of  an  Amiiie.  —  An  amine-molecule 
consists  of  one  or  more  positive  atoms  united  by  nitrogen 
to  hydrogen. 

The  general  formula  of  an  amine  is  R — N=H.2. 

91.  Definition  of  an  Alkalamide. — An  alkalamide- 
molecule  contains  both  positive  and  negative  atoms  united 

by  nitrogen.  H 

—      i       + 
The  general  formula  of  an  alkalamide  is  R— N— R. 

92.  Ammonia  Type. —  An   ammonia -molecule  consists 
of  three  hydrogen-atoms  linked  together  by  nitrogen  thus, 

H 

i 
H — N — H.     By  exchanging  a  portion  of  the  hydrogen  for 

one  or  more  negative  atoms,  an  amide  results ;  for  one  or 
more  positive  atoms  an  amine  is  obtained;  and  for  one  posi- 
tive and  one  negative,  an  alkalamide  results.  These  three 
classes  of  bodies  have  a  structure  similar  to  that  of  ammonia. 
They  are  said  therefore  to  belong  to  the  ammonia  type. 
Amides  and  amines  are  often  regarded  as  compounds  of 

the  monad  radical  (H2N)',  amidogen.  United  to  R,  it  gives 
an  amide  ;  to  R,  an  amine. 

93.  Naming'  of  Derived  Ammonias.  —  Amides   and 
amines  are  called  primary,  secondary,  or  tertiary,  accord- 
ing as  one,  two,  or  three  of  the  hydrogen-atoms  are  replaced. 
The  individual  substances  are  named  by  prefixing  the  Greek 
numerals  to  the  name  of  the  replacing  atom. 


TERNARY  MOLECULES, 


51 


EXAMPLES. — Writing  ammonia  thus 


H) 

,  HlN, 
HJ 


we  may  have 


Primary. 


Cyanamide. 


K) 

H  IN 

HJ 


PotOMamine. 


Secondary. 

Tertiary. 

UN 

HJ 

CI) 

ci  IN 
01  J 

Din-lodamide. 

Tri-chloramide. 

Na) 
Na  IN 
HJ 

Kb) 

Kb  IN 

Rhj 

JM-sodamine. 

Tri-rubidam  inc. 

K) 

K) 

ci  IN 

K     N 

HJ 

cij 

Amide 


Amine 


Alkalamide 


Chloro-potassa  mide.     Chloro-di-potaxsamiffr. 

Amides,  amines,  and  alkalamides,  regarded  as  derivative 
ammonias,  are  called  mon-amides,  di-amides,  tri-amides, 
tetr-amides,  etc.,  according  to  the  number  of  nitrogen- 
atoms  in  the  type. 

EXAMPLES. 


Amide 


Amine 


Alkalamide 


Tertiary  derivatives  are  included  here  because  of  their 
similar  origin.  Many  of  them  really  belong  with  binary 
compounds.  These  bodies  are  sometimes  called  nitriles,  and 
secondary  derivatives  are  sometimes  called  imides. 


Mono. 

Di 

Tri. 

(No2n 

H  IN 

Hj 

(CO)-) 

^ 

(pori 

%h 

Nitryl-mon-amide. 

Carbonyl-di-amide. 

Phoxphoryl-tri-amide. 

Na) 

H  IN 

HJ 

Zn"  ) 

^' 

Biw1 

%h 

Sodio-mon-amine. 

Zinc-di-amine. 

Bismuth-tri-amine. 

Nftl 

IN 
HJ 

(C0)"l 

xh 

ftri 

(Por}M3 

Sodio-iod-amide. 

Mercuro-carbonyl- 
di-amidc. 

Bismuth-phosphoryl- 
tri-amide. 

52 


THEORETIC  A  L  CHE  AILS  77,' I  . 


94.  Mixed  Compounds  of  Hydroxyl  and  Ainido- 
g'eii.  —  As  those  bodies  which  are  formed  on  the  water  type 
may  be  viewed  as  binary  compounds  of  hydroxyl,  and  those 
which  are  formed  on  the  ammonia  type  as  similar  compounds 
of  amidogen,  it  is  evident  that  a  poly-equivalent  radical  may 
combine  with  both  these  residues  at  once,  thus  forming  com- 
pounds intermediate  between  those  of  the  two  groups  men- 
tioned. If  the  poly-equivalent  radical  be  negative,  the  bodies 
produced  are  called  amic  acids  ;  if  positive,  amid-hy- 
drates. 

EXAMPLES.  —  Sulphury!  (SO^)",  the  radical  of  sulphuric  acid,  forms 
in  this  way  sulphamic  acid  (SO2)"  <  \i\ii  ?  «  And  zinc,  a  positive  dyad, 
forms  Zii  |  S  zin  cam  id-hdrate. 


Molecules 


TABULAR  VIEW  OF  MOLECULAR  STRUCTURE. 


ijiKe  At( 

nns       .... 

United  directly 

jcaemei 

Binary 

[  R  and  H, 

Acid 

Unlike 
Atoms 

By  a  Dyad 

j  R  and  H, 

Base 

United 

[  R  and  R, 

Salt 

L  indirectly 

f  - 

1  R  and  H, 

Amide 

.  By  a  Triad 

]  R  and  H, 

Amine 

-          + 

95.  Recapitulation. — I.  Molecules  are  of  two  classes  : 
1st.  Those  composed  of  like  atoms  and  called  Element- 
ary. 

2d.  Those  composed  of  unlike  atoms   and  called  Com- 
pound. 

II.  All  compound  molecules  are  of  two  classes  : 
1st.  Those  whose  atoms  are  directly  united,  called  Binary. 
2d.  Those  whose  atoms  are  indirectly  united,  called  Ter- 
nary. 


TERNARY  MOLECULES.  53 

III.  Ternary  molecules  are  of  two  classes  : 

1st.  Those  in  which  the  linking  atom  is  a  dyad,  called 
Hydrates. 

2d.  Those  in  which  the  linking  atom  is  a  triad,  called 
Compound  Ammonias. 

IV.  Hydrates  are  divided  into  three  classes : 

1st.  Acid  hydrates,  or  acids,  which  consist  of  a  negative 
atom  or  radical,  united  to  hydrogen. 

2d.  Basic  hydrates,  or  bases,  which  consist  of  a  positive 
atom  or  radical,  united  to  hydrogen. 

3d.  Salts,  which  consist  of  a  positive  atom  or  radical, 
united  to  a  negative  atom  or  radical. 

V.  Compound  Ammonias  are  divided  into  three  classes  : 
1st.  Amides,  containing  a  negative  radical  united  to  hy- 
drogen. 

2d.  Amines,  containing  a  positive  radical  united  to  hy- 
drogen. 

3d.  Alkalamides,  containing  a  positive  radical  united  to 
a  negative  radical. 


54  THEORETICAL  CHEMISTRY. 


EXERCISES. 


1.  How  many  atoms  may  a  compound  molecule  contain? 

2.  How  is  the  molecular  mass  of  such  a  molecule  obtained? 

3.  How  many  bonds  may  there  be  in  a  compound  molecule?    How 
many  perissad  atoms? 

4.  Define  a  Binary  molecule,     A  Ternary  molecule. 

5.  Give  the  rule  for  naming  Binaries.     Illustrate  it. 

6.  Platinum  forms  two  compounds  with  bromine;  name  them. 

7.  What  atoms  have  more  than  two  valences? 

8.  What  are  the  oxides  of  phosphorus?     The  chlorides? 

9.  What  are  formulas,  and  how  are  they  written? 

10.  Give  the  formula  of   potassium  iodide;  of  lead  sulphide;   of 
phosphorous  nitride;   of  calcium  chloride;  of  gold  oxide;  of  silver 
arsenide;  of  silicic  bromide;  of  antimorious  oxide. 

11.  Give  the  names  of  NaCl,  SrO.  BiP,  Cu.,As2,  (CS2)2,  (SnO)4. 

12.  How  do  atoms  of  different  valences  combine? 

13    How  are  compound  molecules  formed  from  elemental  ones? 

14.  Define  compound  radicals.     How  are  they  named? 

15.  How  is  variation  in  atomic  valence  explained? 

§2. 

16.  How  are  ternary  molecules  united?     By  what  dyads? 

17.  Define  and  explain  the  general  formula  of  an  acid,  a  base,  and 
a  salt. 

18.  What  is  the  water  type? 

19.  What  compounds   are  formed  by  the  union  of  potassium  to. 
monad,  triad,  pentad,  and  heptad  chlorine  successively,  by  oxygen? 

20.  What  are  the  constituents  of  silver  phosphate;  lithium  carbon- 
ate; zinc  hydrate;  hydrogen  bromate;  rnanganous  phosphate;  mer- 
curous  nitrate?  •*-- 

21.  What  are  the  formulas  of  silicic,  chromic,  iodous,  carbonic,  hypo- 
sulphurous,  bromous,  and  titanic  acids? 

22.  Illustrate  the  formation  of  ternaries  by  direct  union. 

23.  What  is  produced  when  lead  oxide  and  nitrous  oxide  unite? 
bismuthous  and  selenic  oxides?  hydrogen  and  sulphuric  oxides? 


EXERCISES.  55 

24.  How  is  barium  sulphite  produced  by  substitution?     Mercurous 
hypo-chlorite? 

25.  Define  ortho-  and  meta- acids.     How  are  the  latter  derived? 

26.  Which  is  H3PO4?  HC10?  HAsO2?  H2SeO2?  H4WO5? 

27.  Give  the  general  formula  of  the  mona-meta-acid  of  a  triad ;  of 
a  pentad;  of  a  hexad. 

28.  Define  basicity  of  acids.    What  is  a  tetra-basie  and  a  poly-basic 
acid  ? 

29.  What  is  a  poly-acid  base?    What  is  HNaO?  H2BaO.2?  HAuO2? 
H3Bi03? 

30.  How  is  the  name  of  a  salt  derived  from  that  of  an  acid? 
81.  Give  the  rule  for  writing  salt-formulas. 

32.  Write  the  formulas  of  sodium  bromate;  calcium  hypo-chlorite; 
platinic  antimonate;  stannic  chromate;  potassium  borate;  lead  arsen- 
ite;  manganous  carbonate. 

33.  Define  and  illustrate  normal,  acid,  basic,  and  double  salts. 

34.  Distinguisb  an  experimental  from  a  rational  formula. 

35.  Give  the  empirical,  rational,  and  graphic  formulas  of  calcium 
nitrate.     Of  mercurous  phosphate. 

36.  Give  the  formula  of  silver  sulpho-stannate. 

§3. 

37.  What  are  amides?     Amines?     Alkalamides?     How  are  they 
named?     To  what  type  do  they  belong? 

38.  What  is  a  primary  amine?     A  tertiary  di-ainide? 

39.  Write  the  formula  of  sodamine,  chloramide,  sulphamide,  phos- 
phamic  acid. 


56  THEORETICAL  CHEMISTRY. 

CHAPTER   FOURTH. 

VOLUME-RELATIONS  OF  MOLECULES. 

§  1.    RELATION  OF  DENSITY  TO  ATOMIC  MASS. 

96.  Molecular  Volume. — By  the  law  of  Avogadro,  all 
molecules  have  the  same  size ;  that  is,  all  molecules  when  in 
the  gaseous  state  occupy  the  same  volume.     Every  molecular 
formula,  therefore,  not  only  expresses  the  mass  of  the  mole- 
cule, but  also  the  volume  which  it  occupies.     The  molecule 
of  hydrogen  is  taken  as  the  standard  of  molecular  volume ; 
but,  as  it  is  sometimes  convenient  to  speak  of  atomic  volume 
— which,  since  atoms  in  general  can  not  exist  free,  must  be 
a  fiction — the  volume  occupied  by  the  atom  of  hydrogen  is 
taken  as  unity ;  the  volume'  occupied  by  the  molecule  will, 
therefore,  be  two.     Moreover,  as  all  molecules  occupy  the 
same  volume,  the  molecular  volume  of  all  substances  is  as- 
sumed to  be  two,  also. 

97.  Relation  of  Molecular  Mass  to  Density.— Since 
molecular  mass  represents  the  mass  of  two  volumes,  and  rel- 
ative density  represents  the  mass  of  one,  the  relative  density 
of  any  homogeneous  substance  in  the  state  of  gas  is  one  half 
its  molecular  mass. 

EXAMPLES. — Ammonia  gas,  whose  molecular  formula  is  H3N,  has 
a  molecular  mass  of  3-)-14  or  17.  By  the  above  rule,  its  calculated 
relative  density  is  17-=-2  or  8*5;  i.  e.,  it  has  8-5  times  the  mass  of  hydro- 
gen. An  experiment  with  the  balance  shows  that  the  mass  of  one 
liter  of  ammonia  gas  is  0-7627  grams.  As  the  mass  of  one  liter  of 
hydrogen  gas  is  0-0896  grams,  the  relative  experimental  density  of 
ammonia  gas  is  0-7627-=-0-0896  or  8-5. 

98.  Molecular  Mass  Fixed  by  Density.— Conversely, 
knowing  the  relative  density,  the  molecular  mass  may  be 
obtained  by  doubling  it.  \ 


VOLUME -RELATIONS  OF  MOLECULES.  57 

The  analysis  of  any  homogeneous  substance  gives  the  ratio 
of  the  constituents  only,  not  their  absolute  masses.  On  ana- 
lytical grounds,  therefore,  several  molecular  masses,  all  mul- 
tiples of  the  lowest,  may  be  attributed  to  the  body  analyzed. 
By  taking  the  relative  density  of  the  substance  in  the  state 
of  vapor,  however,  and  doubling  it,  the  true  molecular  mass 
is  determined. 

EXAMPLES.— The  analysis  of  hydrogen  oxide — water — shows  that 
in  100  parts  of  it  there  are  88-89  parts  of  oxj'gen  and  11-11  parts  of 
hydrogen.  The  ratio  of  11-11  :  88-89  is  1  :  8.  If  the  molecule  con- 
tain one  part  of  hydrogen  and  eight  parts  of  oxygen,  its  molecular 
mass  will  be  1+8  or  9.  But  it  may  contain  two,  three,  four  or  five 
times  this  quantity  of  each  constituent,  and  yet  yield  the  same  ana- 
lytical results.  Its  molecular  mass,  so  far  as  analysis  goes,  may  be  9, 
18,  27,  36,  45,  etc.  Upon  weighing  now  a  liter  of  water-gas — steam: — 
its  mass  is  found  to  be  0-8047  grams;  whence  its  relative  density  is 
0-8047-5-0-0896,  or  9,  and  its  molecular  mass  is  9X2  or  18.  Water 
therefore  consists  of  2  parts  of  hydrogen  and  16  parts  of  oxygen  in 
each  molecule. 

Again,  olefiant  gas — a  compound  of  carbon  and  hydrogen — affords 
on  analysis  85-71  per  cent  of  carbon  and  14-29  per  cent  of  hydrogen, 
which  is  the  ratio  of  6  :  1.  There  may  be  then  6  parts  of  carbon  to 
one  of  hydrogen  in  the  molecule,  in  which  case  the  molecular  mass 
of  olefiant  gas  will  be  7;  or  12  parts  of  carbon  to  two  of  hydrogen, 
when  it  will  be  14;  or  18  to  3,  giving  21;  or  24  to  4,  giving  28;  the 
ratio  in  all  these  cases  being  the  same.  By  experiment  the  mass  of 
one  liter  of  olefiant  gas  is  1-252  grams.  Its  relative  density  therefore, 
is  1-252 -j-0-0896,  or  14,  and  its  molecular  mass  14X2  or  28.  Hence 
one  molecule  of  olefiant  gas  contains  24  parts  of  carbon  and  4  parts 
of  hydrogen. 

99.  Aid  in  Determining-  Atomic  Mass. — The  atomic 
mass  of  any  simple  substance  is  the  smallest  mass  of  it  which 
can  enter  into  the  formation  of  a  molecule.  By  ascertain- 
ing, therefore,  the  molecular  masses  of  various  compounds 
of  the  same  element,  and  by  comparing  together  the  masses 
of  this  element  which  they  severally  contain,  it  is  easy  to  fix 
its  atomic  mass. 


58  THEORETICAL  CHEMISTRY. 

EXAMPLES. — A  molecule  of  water  contains  16  parts  of  oxygen ;  a 
molecule  of  carbonic  gas,  32  parts ;  a  molecule  of  sulphuric  oxide,  48 
parts;  etc.  In  no  known  compound,  however,  is  there  less  than  16 
parts  of  oxygen  in  a  molecule;  16  is  therefore  the  atomic  mass  of 
oxygen. 

Again,  a  molecule  of  marsh-gas  contains  12  parts  of  carbon,  a 
molecule  of  olefiant  gas  24,  a  molecule  of  glycerin  36,  a  molecule  of 
tartaric  acid  48,  a  molecule  of  citric  acid  72.  The  smallest  of  these 
numbers,  12,  is  therefore  the  atomic  mass  of  carbon;  and  the  bodies 
above  mentioned  contain  in  each  molecule,  one,  two,  three,  four,  five, 
and  six  atoms  of  carbon,  respectively. 


§  2.    RELATION  OF  GASEOUS  DIFFUSION  TO  ATOMIC  MASS. 

100.  Gaseous  Diffusion. — In  1825,  Dobereiuer,  having 
collected  some  hydrogen  gas  in  a  cracked  jar,  standing  over 
water,  noticed  that  the  level  of  the  water  within  the  jar  rose 
one  and  a  half  inches  in  twelve  hours ;   a  result  obviously 
due  to  the  escape  of  the  hydrogen  through  the  crack.     Gra- 
ham found,  on  repeating  the  experiment,  that  as  the  hydro- 
gen escaped  outward,  a  portion  of  air,  much  less  in  amount, 
entered  the  jar.     And  on  investigation  he  ascertained  that 
gases,  even  when  separated  by  porous  partitions,  pass  freely 
into  each  other.     This  mutual  passage  of  one  gas  into  an- 
other is  called  diffusion. 

101.  Graham's  Law  of  Diffusion. —  Graham  showed 
experimentally  that  the  rapidity  with  which  different  gases 
diffuse  into  each  other  varies  for  each  gas ;    and  also  that 
this  rapidity  stands  in  intimate  relation  to  the  relative  den- 
sity of  the  gas.     This  relation  is  expressed  in  the  following 
law : 

The  velocity  of  the  diffusion  of  any  gas  is  inversely 
proportional  to  the  square  root  of  its  relative  density. 

102.  Explanation  of  Diffusion. — Physics  assumes  that 
all  gaseous  molecules  are  in  rapid  motion  in  straight  lines. 
Now,  as  the  pressure  upon  all  gaseous  volumes  is  equal — 


(iASKOm  DIFFUSION.  59 

being  the  atmospheric  pressure — and  as  this  pressure  is  ex- 
actly balanced  by  the  elasticity  of  the  gas — due  to  the  direct 
outward  impact  of  its  molecules — it  follows,  from  Avogadro's 
law,  that  the  impact  of  all  gaseous  molecules  is  equal. 

Moreover,  iu  dynamics,  impact  is  proportional  to  the 
product  of  the  mass  into  the  square  of  the  velocity.  Since, 
therefore,  molecules  differ  in  mass,  it  is  obvious  that  the 
lighter  ones  must  move  faster  than  the  more  massive  ones, 
to  produce  the  same  effect.  If  one  molecule  has  four  times 
the  mass  of  another,  the  latter  needs  to  move  twice  as  fast 
to  strike  the  same  effective  blow ;  since  4  times  I2  is  the 
same  as  once  22,  both  being  4.  By  the  supposition,  the  masses 
of  the  molecules  are  as  4  :  1  ;  their  velocities  therefore  must 
be  as  1  :  2.  Hence  their  velocities  are  inversely  as  the  square 
roots  of  their  molecular  masses ;  or,  what  is  the  same  thing, 
of  their  relative  densities;  which  is  the  law7  of  diffusion,  de- 
duced by  Graham  from  experiment. 

EXAMPLES. — The  relative  density  of  oxygen  being  16,  a  molecule 
of  oxygen  has  16  times  the  mass  of  a  molecule  of  hydrogen.  The 
elasticity  of  both  gases  under  the  atmospheric  pressure  is  the  same. 
But,  that  the  impact  should  be  the  same,  the  lighter  or  hydrogen  mol- 
ecule must  move  4  times  as  fast  as  the  more  massive  or  oxygen  mole- 
cule, since 

OXYGEN.  HYDROGEN. 

Mass.      Veloc.         Mass.      Veloc. 

16    x    I2     =     1    X    42 

That  is,  hydrogen  molecules  should  move  with  four  times  the  velocity 
of  oxygen  molecules. 

Using  a  thin  graphite  plate  as  a  partition,  Graham  found  experi- 
mentallv,  that,  taking  air  as  unity,  the  ratio  of  the  diffusion  of  oxygen 
is  to  that  of  hydrogen  as  0-95  :  3-83.  But  0-95  :  3-83  .:  :  1  :  4.  As  a 
matter  of  fact,  therefore,  hydrogen  molecules  do  move  4  times  faster 
than  oxygen  molecules. 

1O3.  Determination  of  Molecular  Mass  by  Diffu- 
sion.— If  the  velocity  of  diffusion  of  any  gas  is  equal  to  the 
inverse  square  root  of  its  relative  density,  then  the  relative 


00  THEOUETK'M. 

density  of  any  gas  must  be  equal  to  the  inverse  square  of 
its  velocity  of  diffusion.  Or  mathematically, — calling  V  the 

velocity  of  diffusion  and  D  the  relative  density — if  V=  ~;,  _" 
then  D=y^.  Of  course,  by  doubling  the  relative  density 
thus  given,  the  molecular  mass  is  obtained. 

EXAMPLES. — By  Graham's  table  of  diffusibilities,  carbonic  gas  has 
a  diffusive  power  of  0-812  as  compared  with  air,  or  of  0-212  as  com- 
pared with  hydrogen.  ButD— y^;  hence  D  =  ..ish'2  =;  22-22.  The 

relative  density  of  carbonic  gas  being  22-22,  its  molecular  mass  must 
be  22-22X2  or  44-44.  Analysis  shows  it  to  be  22,  41,  66,  88,  etc.  Dif- 
fusion fixes  it  as  the  second  of  these  numbers.  It  was  in  this  way 
that  Soret  determined  the  relative  density,  and  thence  the  molecular 
mass,  of  ozone. 

§  3.    COMBINATION  BY  VOLUME. 

104.  Law  of  Combination  by  Volume. — The  propor- 
tions in  which  gaseous  volumes  enter  into  combination  were 
first  investigated  by  Gay-Lussac.     His  law  asserts : 

1st.  That  the  ratio  in  which  gases  combine  by  volume 
is  always  a  simple  one  ;  and 

2d.  That  the  volume  of  the  resulting-  gaseous  product 
bears  a  simple  ratio  to  the  volumes  of  its  constituents. 

105.  Deduction  of  this  Law. — The  law  of  combina- 
tion by  volume,  which,  in  Gay-Lussac's  time,  was  purely  ex- 
perimental, has  been  recently  shown  by  Clausius  to  be  a  very 
simple  deduction  from  the  law  of  Avogadro. 

According  to  Avogadro's  law,  equal  volumes  of  all  gases 
contain  the  same  number  of  molecules.  If,  therefore,  the 
number  of  molecules  be  in  any  way  diminished,  the  vol- 
ume itself  will  be  diminished  proportionally.  Suppose  now, 
that  in  the  given  volume  of  any  gas,  each  molecule  is  di- 
atomic, i.  e.,  contains  but  two  atoms;  then,  if  by  any  means 
the  molecule  can  be  made  tetr-atomic,  i.  e.,  four-atomed, — 
the  absolute  number  of  atoms  remaining  the  same — the  nuni- 


nij'MK.  61 

ber  of  molecules  will  be  reduced  one  half,  since  each  mole- 
cule contains  twice  as  many  atoms.  But  by  this  reduction 
in  the  number  of  molecules  a  corresponding  diminution  in 
volume  takes  place,  and  the  volume  of  the  gas  is  reduced 
one  half  also. 

Again,  if  the  di-atomic  molecule  become  tri-atomic,  the 
number  of  molecules  would  be  reduced  by  one  third.  Hence, 
the  volume  originally  occupied  by  these  molecules  would  be 
reduced  in  the  same  ratio. 

1O6.  Application  of  Clausius's  Theory. — To  apply 
this  reasoning  to  the  facts  of  volume-combinations,  let  us 
consider  separately  the  combinations  which  hydrogen  forms 
with  the  four  valence  groups,  monads,  dyads,  triads,  and 
tetrads,  supposing  their  molecules  to  be  all  di-atomic. 

FIRST  CASE. — In  the  case  of  monads,  one  atom  combines 
with  one  atom  of  hydrogen ;  and  since  the  molecules  of  both 
are  di-atomic,  a  molecule  will  combine  with  one  molecule, 
and  a  volume  with  one  volume  of  hydrogen.  All  bodies 
consisting  of  di-atomic  molecules  made  up  of  monad  atoms, 
combine,  therefore,  in  equal  volumes. 

Further,  when  the  monad  atom  and  the  hydrogen-atom 
combine,  they  form  a  di-atomic  molecule  precisely  like  a  mol- 
ecule of  either  of  its  constituents,  except  that  its  atoms  are 
unlike.  The  two  di-atomic  simple  molecules  form  two  di- 
atomic compound  molecules.  Two  volumes  of  simple  gases 
give  two  volumes  of  a  compound  gas. 

Substances  of  the  first  class,  then, — i.  e.,  monads  —  com- 
bine with  each  other  volume  to  volume,  and  yield  two  vol- 
umes of  the  product. 

EXAMPLES. — A  chlorine  atom  01,  unites  with  a  single  hydrogen 
atom  H,  to  form  HC1,  both  being  monads.  As  the  molecules  of  both 
are  di-atomic,  these  sabstances  unite  molecule  to  molecule,  or  volume 
to  volume.  On  mixing  the  volume  of  chlorine  with  the  volume  of 
hydrogen  and  exposing  them  to  sunlight,  they  unite  to  form  hydro- 
gen chloride  gas,  each  molecule  of  which  is  di-atomic,  containing  one 


62 


THEORE  TIC  A  L  CHEMIS  Til 1 '. 


chlorine  atom  and  one  hydrogen  atom.  The  number  of  molecules 
after  the  union  being  the  same  as  before,  the  volumes  are  unaffected. 
To  represent  it  molecularly: 

H  Cl  H-C1 

and       |      give 


A 


Or  in  volumes, — 


and 


Cl., 


H— Cl 


yield 


SECOND  CASE. — If  the  atom  taken  be  a  dyad,  then  it  will 
unite  with  tvvo  atoms  of  hydrogen;  or  one  molecule  will 
unite  with  two  molecules,  or  one  volume  with  two  volumes. 
Dyads,  therefore,  combine  with  monads  in  the  ratio  of  one 
volume  to  two  volumes. 

Moreover,  the  molecule  which  results  from  the  union  of 
one  dyad  atom  with  two  monad  atoms  will  be  tri-atomic. 
As  before  union  they  were  di-atomic,  three  molecules  then, 
make  but  two  now.  The  total  number  of  molecules  is  one 
third  less  than  before ;  and,  of  course,  the  volume  is  dimin- 
ished in  the  same  ratio.  Two  volumes  of  one  gas  and  one 
volume  of  the  other  give  three  volumes ;  after  combination, 
but  two  volumes  remain.  So  that  three  volumes  of  simple 
gases  give  two  volumes  of  a  compound  gas,  a  condensation 
of  three  volumes  to  two  taking  place  during  union. 

Substances  of  the  second  class,  then, — i.  e.  dyads  —  com- 
bine with  monads  in  the  ratio  of  one  volume  to  two,  and 
yield  two  volumes  of  the  product. 

EXAMPLES. — The  atom  of  oxygen  is  bivalent;  its  molecule  is  di- 
atomic. Assuming  a  fixed  number  of  molecules  in  the  given  volume, 
say  100,  then  the  200  atoms  in  these  100  molecules  will  unite  with  400 
atoms,  or  200  molecules  of  hydrogen,  producing  600  atoms.  In  other 
words,  one  volume  of  oxygen  will  combine  with  two  volumes  of  hy- 
drogen. Now  the  water-molecule  which  results  contains  3  atoms,  2 


COMBINATION  BY  rOLUMK.  63 

of  them  hydrogen  and  one  oxygen ;  the  GOO  atoms  of  these  substances 
above  mentioned  will  therefore  give  200  water-molecules,  which,  by 
the  assumption  above,  occupy  two  volumes.  Hence  one  volume  of 
oxygen  and  two  volumes  of  hydrogen  yield  two  volumes  of  water-gas. 

THIRD  CASE. — One  triad  atom  unites  with  three  monad 
atoms,  one  molecule  with  three  molecules,  one  volume  with 
three  volumes.  The  original  simple  molecules  contain  two 
atoms,  the  resulting  compound  molecule,  four;  the  number 
of  molecules,  and  hence  the  corresponding  volume,  is  there- 
fore reduced  one  half,  four  volumes  being  condensed  into 
two. 

Substances  of  the  third  class,  L  e.,  triads,  unite  with  mon- 
ads in  the  ratio  of  one  volume  to  three,  and  yield  two  vol- 
umes of  the  product. 

EXAMPLES. — One  atom  of  nitrogen  unites  with  three  atoms  of  hy- 
drogen to  form  ammonia.  One  molecule  of  nitrogen  and  tlnee  mole- 
cules of  hydrogen  give  two  molecules  of  ammonia. 

N  HHH  HHH  N 

HI      and        |     |     |       give     * , ' • s 

N  HHH  N  HHH 

Four  di-atomic  give  two  tetr-atomic  molecules.  Hence  one  volume 
of  nitrogen  and  three  volumes  of  hydrogen  form  two  volumes  of  am- 
monia gas. 

FOURTH  CASE. — Lastly,  one  tetrad  atom  unites  with  four 
monad  atoms,  one  tetrad  molecule  with  four  monad  mole- 
cules, one  volume  of  any  tetrad  with  four  volumes  of  any 
monad.  The  resulting  molecule  contains  five  atoms,  and 
hence  the  five  original  volumes  are  condensed  to  two. 

Substances  of  the  fourth  class,  i.  e.,  tetrads,  unite  with 
monads  in  the  ratio  of  one  volume  to  four,  and  yield  two 
volumes  of  the  product. 

EXAMPLES. —One  atom  of  carbon  and  four  atoms  of  hydrogen 
unite  to  form  marsh  gas.  That  is,  C.2  and  (H2)4  give  (H4C)2;  or  five 
di-atomic  give  two  pent-atomic  molecules.  Hence  one  volume  of 
carbon  gas  and  four  volumes  of  hydrogen  form  two  volumes  of  marsh 
gas. 


64 


THEORE  TIC  A  L  CTIEMISTR  F. 


1O7.  Recapitulation  of  Volume-combinations. — The 

various  ratios  in  which  combinations  by  volume  take  place 
according  to  Gay-Lussac's  law,  may  be  thus  represented  : 


X  fiT  VOLUME.  65 

These  results  correspond  precisely  with  those  required  by 
the  law  of  combination  by  valence,  which,  for  the  union  of 
di-atomic  molecules,  gives  the  following  four  cases : 

1  molecule  and  1  molecule    give  2  molecules. 

1  molecule  and  2  molecules  give  2  molecules. 

1  molecule  and  3  molecules  give  2  molecules. 

1  molecule  and  4  molecules  give  2  molecules. 

Or,  written  out  fully  to  express  the  atomic  character  of 

the  molecule : 

Molecules  Di-atomic. 

1  monad  molecule  and  1  monad  molecule  give  2  di-atomic  molecules. 
1  dyad  molecule  and  2  monad  molecules  give  2  tri-atomic  molecules. 
1  triad  molecule  and  3  monad  molecules  give  2  tetr-atomic  molecules. 
1  tetrad  molecule  and  4  monad  molecules  give  2  pent-atomic  molecules. 

1O8.  Cases  where  the  Elemental  Molecules  are  not 
Di-atomic. — The  cases  of  this  are  practically  but  two  in 
number;  one  where  the  molecule  is  mon-atomic,  the  other 
where  it  is  tetr-atomic. 

FIRST  CASE. — All  known  mon-atomic  molecules  are  dyads. 
Hence  the  atomic  combination  with  monad  atoms  would  be : 

1  atom  and  2  atoms  give  3  atoms. 
And  by  molecules : 

1  molecule  and  1  molecule  give  1  molecule. 
Or  by  volumes : 

1  volume  and  1  volume  give  1  volume. 

That  is,  mon-atomic  dyad  molecules  combine  with  di- 
atomic monad  molecules  in  the  ratio  of  equal  volumes,  yield- 
ing one  volume  of  the  product. 

EXAMPLES. — The  dyads  zinc  and  mercury  have  mon-atomic  mole- 
cules. One  atom  of  zinc  unites  with  two  atoms  of  chlorine  to  form 
zinc  chloride;  that  is,  one  mon-atomic  zinc  molecule  unites  with  one 
di-atomic  molecule  of  chlorine,  to  form  one  tri-atomic  molecule  of 
zinc  chloride.  As  all  molecules  have  the  same  size,  this  is  equivalent 
to  saying  that  one  volume  of  zinc-vapor  and  one  volume  of  chlorine 
gas  combine  to  give  one  volume  of  zinc  chloride  vapor,  a  condensa- 
tion of  one  half. 


66 


THEORETICAL  CHEMISTRY. 


SECOND  CASE. — All  known  tetr-atomic  molecules  are  tri- 
ads. The  atomic  combination  with  monads  would  therefore 

be: 

1  atom  and  3  atoms  give  4  atoms. 

And  by  molecules : 

1  tetr-atomic  molecule  and  6  di-atomic  molecules  give  4  tetr-atomic 
molecules. 

Or  by  volumes: 

1  volume  and  6  volumes  yield  4  volumes. 

That  is,  tetr-atomic  triad  molecules  combine  with  di-atomic 
monad  molecules  in  the  ratio  of  one  volume  to  six  volumes, 
yielding  four  volumes  of  the  product,  a  condensation  of  seven 
volumes  to  four. 

EXAMPLES. — Phosphorus  is  a  triad,  having  a  tetr-atomic  molecule. 
When  it  unites  with  chlorine  we  have  atomically,  P  and  C13  give 
PCI.,;  molecularly,  P^  and  (C12)6  give  (PC13)4,  or  by  volume: 


Cl, 


OL 


PCI, 


PC13 


1O9.  Tri-atomic  and  Hex-atomic  Molecules. —  The 

law  of  combination  by  volume  for  tri-atomic  and  hex-atomic 
molecules,  should  any  substances  be  found  to  combine  in 
this  way,  can  easily  be  deduced  from  the  principles  already 
given. 

The  entire  foregoing  chapter  furnishes  an  excellent  illus- 
tration of  the  intimate  mutual  relations  between  Physics  and 
Chemistry.  Assuming  either  the  physical  or  the  chemical 
data  at  pleasure,  the  other  can  be  deduced  from  it. 


EXERCISES.  67 


EXERCISES. 
§*• 

1.  What  is  molecular  volume,  and  how  is  it  expressed? 

2.  The  mass  of  one  liter  of  carbonic  gas  (CO2)  is  1-97  grams;  what 
is"  its  calculated,  and  what  its  experimental,  relative  density? 

3.  Of  what  assistance  is  relative  density  in  fixing  a  molecular 
mass  ? 

4.  Iron  chloride  contains  34-46  per  cent  of  iron,  and  65-54  per  cent 
of  chlorine  ;   its  relative  density  is  81  ;  what  is  its  molecular  mass  ? 
How  much  iron  and  how  much  chlorine  is  there  in  each  molecule? 

5.  How  is  an  atomic  mass  determined  by  relative  density? 

6.  Hydrogen  bromide  contains  1-24  per  cent  of  hydrogen,  and  98*76 
of  bromine  ;  its  relative  density  is  40-38.     Mercury  bromide  contains 
56-56  per  cent  of  mercury  and  44-44  of  bromine;  its  relative  density 
is  179-6.    Boron  bromide  contains  4-38  per  cent  of  boron,  95-62  of  bro- 
mine;   its  relative  density  is  125-12.     Silicon  bromide  contains  8-04 
per  cent  of  silicon  and  91-96  of  bromine;  its  relative  density  is  173-5. 
What  is  the  atomic  mass  of  bromine  ? 


7.  What  is  gaseous  diffusion?     Give  Graham's  law. 

8.  How  is  the  fact  of  diffusion  explained?     Illustrate. 

9.  How  is  molecular  mass  fixed  by  diffusion? 

10.  Marsh-gas  has  a  diffusibility  of  0.35,  that  of  hydrogen  being  1  ; 
what  is  its  molecular  mass  ? 

§3. 

11.  Give  Gay-Lussac's  law  of  combination  by  volume. 

12.  How  may  this  be  derived  from  the  law  of  Avogadro? 

13.  How  do  monads  combine  with  hydrogen  by  volume?     Dyads? 
Triads?     Tetrads? 

14.  In  what  proportion  by  volume,  do  tetrad  sulphur  and  oxygen 
unite?    What  volume  has  the  product? 

15.  Do  the  volume-combinations  as  deduced  from  the  law  of  valence 
agree  with  those  observed  by  Gay-Lussac  ? 

16.  How  do  merourv  and  arsenic  unite  bv  volume? 


68  THEORETICAL  CEEM1STKT. 


CHAPTER    FIFTH. 

CHEMICAL  REACTIONS.     STOICHIOMETRY. 
§  1.    CHEMICAL  EQUATIONS. 

110.  Molecular  Stability. — All  material  molecules  are 
more  or  less  liable  to  chemical  change.     The  atoms  within 
them  may  be  altered  in  kind,  in  number  or  in  relative  posi- 
tion, by  various  external  influences.     A  molecule  is  the  more 
stable  in  proportion  as  it  resists  this  tendency  to  change. 

111.  Chemical  Reactions. — Any  mutual  action  which 
takes  place  between  the  atoms  composing  a  molecule  is  called 
a  Chemical  Re-action.     Both  of  the  substances  acting  are 
called  Re-agents. 

EXAMPLES. — "When  a  candle  burns,  the  wax  and  the  oxygen  of 
the  air  act  mutually  upon  each  other,  yielding  gaseous  products  en- 
tirely unlike  the  wax  or  the  oxygen.  When  gunpowder  explodes  the 
various  molecules  which  it  contains  react  upon  each  other,  and  a  new 
set  of  products  is  the  result.  When  the  components  of  a  Seidlitz 
powder  are  mixed  together  and  moistened,  they  react  upon  each  other, 
producing  the  well-known  effervesce  nee. 

112.  Reactions  Always  Molecular. — Chemical  reac- 
tions always  take  place  within  the  molecule.    When,  there- 
fore, two  substances  react  upon  each  other,  the  changes  which 
result  may  be  viewed  as  taking  place  between  single  mole- 
cules of  each.     Moreover,  since  all  molecules  in  homogene- 
ous matter  are  alike,  and  what  is  true  of  one  molecule  is 
true  of  any  mass  of  them,  it  follows  that  a  molecular  change 
represents  accurately  a  mass-change. 

113.  Reactions  Expressed  by  Formulas. — Every  for- 
mula in  Chemistry  represents  a  molecule ;  and  as  all  reac- 
tions are  viewed  as  taking  place  between  molecules,  these 


CHKMK'A  L  !<:<  f  .  /  T/OXS.  69 


reactions  may  be  represented  by  the  use  of  molecular  for- 
mulas. 

114.  Chemical   Equations.  —  Chemical   reactions  are 
usually  represented  in  the  form  of  equations  ;  the  substances 
entering  into  the  reaction  —  called  factors  —  constituting  the 
h'rst  member,  and  those  issuing  from  it  —  called  products  — 
the  second. 

AVhen  two  molecules  act  upon  each  other,  the  equation 
representing  the  reaction  may  be  written  by  the  following 
rule  : 

Place  the  formulas  of  the  factors  —  connected  by  the 
sign  plus  —  as  the  first  member  of  the  equation,  and  the 
formulas  of  the  products  —  also  connected  by  the  sign 
plus  —  as  the  second. 

EXAMPLES.  —  The  reaction  of  the  two  molecules  AB  and  CD  would 
be  represented  thus  : 

AB  -f  CD  =  AD  -f  CB. 

Sometimes,  though  rarely,  the  minus  sign  is  used  in  an  equation,  thus: 
ABC  —  B  =  AC. 

115.  Masses  of  the  Factors  and  the  Products  Equal. 

As  each  formula  represents  a  definite  mass  of  matter  —  the 
molecular  mass  —  it  follows  that  the  masses  of  matter  taking 
part  in  a  chemical  change  are  perfectly  definite.  And,  more- 
over, since  the  atoms  are  the  same  after  the  reaction  as  be- 
fore it  —  being  only  differently  associated  —  it  also  follows  that 
no  loss  of  matter  can  be  the  result  of  any  chemical 
reaction.  The  sum  of  the  molecular  masses  of  the  prod- 
ucts must,  therefore,  always  equal  the  sum  of  the  molecular 
masses  of  the  factors. 

116.  Meaning'  of  the  Signs.  —  The  equality  sign  indi- 
cates the  equality  in  mass  of  both  members  of  the  equation. 
The  plus  sign  means  simply  "and,"  and  signifies  that  the 
molecules  thus  united  are  mixed  together.     The  minus  sign 
means  "  from,"  and  indicates  the  removal  of  a  simpler  group 
of  atoms  from  a  more  complex  one. 

0 


70  THEORETICAL  CHEMISTRY. 

117.  Construction  of  Equations.  —  Ordinarily  the  rule 
above  given  is  quite  sufficient  for  the  construction  of  an  equa- 
tion, the  number  of  molecules  involved  being  determinable 
by  inspection.  In  some  cases,  however,  where  the  reaction 
is  a  complex  one,  it  is  convenient  to  be  able  to  calculate 
the  number  of  molecules.  This  may  readily  be  done  by  the 
use  of  the  algebraic  method  of  simultaneous  linear  equa- 
tions, which  may  be  illustrated  as  follows  :  *  Suppose  it  be 
required  to  write  the  reaction  where  tin  acts  on  nitric  acid, 
the  products  being  stannic  oxide,  nitrogen  di-  oxide,  and 
water.  Using  letters  to  indicate  the  number  of  molecules, 
we  have  the  equation  : 

Sna+  (HN03)6=  (Sn02)w+  (N2O2)*+  (H2O), 
Since  the  number  of  atoms  of  each  element  must  be  the 
same  on  the  two  sides  of  the  equation,  we  have  for  the  tin 
a=w;  for  the  hydrogen,  b=2y;  for  the  nitrogen,  b=2x;  and 
for  the  oxygen,  3b=2w+2x+y.  Assuming  6=1,  and  solv- 
ing these  equations,  we  find  a=f,  #=J,  y=\  and  w=f  ;  or, 
clearing  of  fractions,  a=3,  6=4,  w=3,  x=2  and  ?/=2.  Sub- 
stituting these  numerical  values  now  for  the  literal  ones 
above  given,  we  have  the  correct  equation  : 

Sn3+  (HN03)4=  (Sn02)3+  (N,Of), 


118.  Classification  of  Reactions.  —  Chemical  reactions 
are  usually  divided  into  three  classes,  as  follows  : 

1st.  Analytical  reactions  ;  which  represent  the  separa- 
tion of  a  complex  molecule  into  simpler  ones. 

2d.  Synthetical  reactions  ;  which  represent  the  union  of 
two  or  more  simple  molecules,  to  form  a  more  complex  one. 

3d.  Metathetical  reactions  ;  which  represent  a  transpo- 
sition or  exchange  of  atoms  between  molecules. 

EXAMPLES.  —  Analytical  reactions  may  be  represented  by  the  gen- 
eral equation:  AB  =  A  -j-  B. 

*As  suggested  by  C.  E.  Munroe. 


\li(  'A  L  A'V  HA  T10NS.  1  1 


Or,  to  take  an  actual  example, 

(NH4)N03  N20         +  '       (H20)2 

Ammonium  nitrate.  Nitrogen  oxide.  Water. 

which  is  read  thus:  One  molecule  of  ammonium  nitrate  yields  one 
molecule  of  nitrogen  oxide  and  two  molecules  of  water. 

Synthetical  reactions  are  the  reverse  of  analytical  ;  they  are  repre- 
sented by  the  general  equation: 

A  +  B  =  AB. 
Or,  as  an  actual  example, 

CaO          +  SO,  CaS04 

Calcium  oxide.          Sulphuric  oxide.  Calcium  sulphate. 

read  thus:  One  molecule  of  calcium  oxide  and  one  molecule  of  sul- 
phuric oxide  yield  one  molecule  of  calcium  sulphate. 

Metathetical  reactions  —  from  perori&tyu,  to  displace  or  transpose  — 
are  represented  by  the  general  formula: 

AB  +  CD  =  AD  +  £§. 

Or,  practically,  by  the  equation: 

Ag(N03)       +       NaCl  AgCl        +       Na(NO3) 

Silver  nitrate.         Sodium  chloride.         Silver  chloride.         Sodium  nitrate. 

A  molecule  of  silver  nitrate  reacts  upon  a  molecule  of  sodium  chlo- 

ride, to  produce  one  molecule  of  silver  chloride  and  one  of  sodium 

nitrate;  an  exchange  taking  place  between  positive  atoms. 

In  all  the  above  examples,  each  letter  in  the  general  equa- 
tions, and  each  formula  in  the  special,  represents  an  entire 
molecule.  Less  than  an  entire  molecule  can  not  enter  into, 
or  issue  from,  any  chemical  reaction. 

119.  Conditions   Favoring-   Chemical  Change.  —  Fa- 
cility of  chemical  change  depends,  to  a  large  extent,  upon 
the  ease  with  which  the  atoms  of  any  molecule  may  be  re- 
arranged.    It  is  found,  for  example,  that  chemical  changes 
take  place  very  readily  when  the  substances  acting  are  in 
the  liquid  or  gaseous  state.     Hence  fusion,  or  solution,  by 
which  bodies  are  liquefied,  or  vaporization,  by  which  they 
are  converted  into  gases,  facilitate  chemical  action. 

120.  Berthollet's  Laws.  —  Those  conditions  of  chemical 
change  which  depend  upon  solubility  are  stated  in  the  fol- 
lowing general  law,  first  established  by  Berthollet  : 


72  THEORETICAL  CHEMISTRY. 

Whenever,  on  mixing  two  substances  in  solution,  a 
compound  can  be  formed  by  a  re-arrangement  of  their 
atoms,  which  is  insoluble  in  the  menstruum  employed, 
such  compound  will  be  formed,  and  will  appear  as  a 
precipitate. 

EXAMPLES.— If  AB  be  dissolved  in  water,  and  CD,  also  dissolved 
in  water,  be  added  to  it,  then  any  re-arrangement  must  obviously  pro- 
duce AD  and  CB.  AB  and  CD  are  soluble  in  water;  but  AD,  or  CB, 
or  both,  may  be  insoluble.  In  either  case,  the  new  and  insoluble  com- 
pound will  separate  from  the  solution  in  the  solid  form,  the  liquid 
losing  its  clearness  and  becoming  turbid. 

The  solid  substance  which  thus  separates  from  a  solution 
is  called  a  precipitate.  Any  substance  which  will  produce 
a  precipitate  when  added  to  a  solution  of  any  other  substance 
is  called  a  precipitant.  The  process  of  producing  a  precipi- 
tate is  called  precipitation. 

121.  Precipitation  both  Chemical  and  Physical. — 
The  first  step  in  precipitation  is  the  re-arrangement  of  the 
atoms ;  this  is  a  chemical  result.    The  second  step  is  the  sep- 
aration of  the  insoluble  product ;  this  depends  on  the  adhe- 
sion between  the  liquid  molecules  and  those  of  the  solid,  and 
hence  is  a  physical  result.     No  conclusion  can  be  drawn, 
therefore,  as  to  the  intensity  of  the  chemism,  from  the  mere 
fact  of  precipitation. 

122.  Law  of  Gaseous  Change. —  The  second  law  of 
BerthoTlet  holds  when  the  product  of  the  reaction,  instead 
of  being  a  solid  and  insoluble,  is  a  gas.     It  may  thus  be 
stated : 

Whenever,  by  the  action  of  bodies  upon  each  other, 
any  substance,  volatile  at  the  temperature  of  the  ex- 
periment, can  be  formed  by  a  re-arrangement  of  the 
atoms,  such  re -arrangement  will  take  place,  and  such 
substance  will  be  evolved  as  a  gas  or  vapor. 

EXAMPLES. — Theoretically,  as  above,  AB  and  CD,  by  rearrange- 
ment, give  AD  and  CB.  If  AD  or  CB  is  volatile  at  the  temperature 


CHEMICAL  EQUATIONS.  73 

of  the  experiment,  it  will  separate  from  the  solution  in  the  gaseous 
form.  Or,  actually,  let  Na2(CO3)  and  H2(S04)  be  mixed  together  in 
solution.  By  the  chemical  re-arrangement,  Na.2(SO4)  and  H2(CO3) 
will  be  produced.  As,  however,  the  body  H2(CO3)  can  not  exist  at 
ordinary  temperatures,  it  separates  into  H2O  and  C02;  which  latter 
substance,  being  a  gas,  escapes  from  the  solution. 

Again,  on  mixing  together  potassium  nitrate  K(NO3)  and  hydro- 
gen sulphate  H2(j3O4),  there  will  result  by  the  re-arrangement,  the 
bodies  HK(SO4)  and  H(NO3) — hydro-potassium  sulphate,  and  hydro- 
gen nitrate ;  this  being  the  chemical  part  of  the  change.  If  now  heat 
be  applied  to  the  mixture,  the  nitric^  acid,  being  volatile,  will  escape 
as  a  vapor. 

The  rapid  escape  of  a  gas  from  a  liquid,  such  as  is  noticed 
in  mixing  Seidlitz  powders,  for  example,  is  called  efferves- 
cence. 

123.  Prediction  of  Results. —  Whether  a  chemical 
change  will  actually  take  place  or  not  may,  in  many  cases, 
be  predicted  by  means  of  these  laws,  if  the  properties  of 
the  products  be  known.  i3y  the  use  of  a  table  —  given  in 
the  appendix — showing  the  solubility  of  various  substances, 
all  cases  under  the  first  law  may  be  predicted ;  and  by  hav- 
ing some  familiarity  with  the  volatility  of  various  bodies, 
cases  may  be  predicted  under  the  second  law. 

EXAMPLES. — If  calcium  chloride  and  sodium  carbonate  be  mixed 
in  solution,  will  there  bj  a  precipitate?  The  reaction  is  thus  written: 

CaCl2  +  Na2(C03)  =  Ca(CO.{)  +  (NaCl)2 

Referring  to  the  table,  it  will  be  seen  that  Ca(C03)  calcium  carbonate, 
is  insoluble.  It  will  therefore  separate  in  the  solid  form  and  fall  as  a 
precipitate. 

If,  however,  an  acid  be  at  the  same  time  formed,  and  the  solid  sub- 
stance be  soluble  in  acids,  there  will  be  no  precipitate.  If  hydrogen 
sulphide  and  ferrous  sulphate  be  mixed  in  solution,  the  reaction  would 
be  represented  by  the  equation: 

H2S  +  Fe(S04)  =  FeS  -f  H2(SO4) 

By  the  table,  ferrous  sulphide  (FeS),  though  insoluble  in  water,  is 
soluble  in  acids.  Were  water  alone  present,  this  substance  would  be 


74  THEORETICAL  CHEMISTRY. 

precipitated;  but  as  sulphuric  acid  (H2(SO4))  is  in  the  solution,  being 
set  free  in  the  reaction,  there  will  be  no  precipitate. 

Again,  if  ammonium  sulphate  and  calcium  carbonate  be  heated 
together,  will  there  be  a  change?  The  only  possible  exchange  is  the 
following: 

(NH4)2(S04)    +    Ca(COs)    =  (NH4)2(CO3)    +    Ca(SO4) 
Ammonium  Calcium  Ammonium  Calcium, 

sulphate.  carbonate.  carbonate.  sulphate. 

But  ammonium  carbonate  is  volatile;  it  will  therefore  escape  in  vapor, 
leaving  the  calcium  sulphate  behind. 

124.  Modes  of  Chemical  .Action. — Chemical  changes 
in  matter  may  take  place  in  five  different  ways,  namely : 

1.  By  the  direct  union  of  simpler  molecules  to  form  a  more 
complex  one. 

2.  By  the  separation  of  a  complex  molecule  into  simpler 
ones. 

3.  By  the  substitution  in  a  molecule  of  one  atom  or  group 
of  atoms  for  another  or  for  several  others. 

4.  By  the  mutual  exchange  of  atoms  between  molecules. 

5.  By  the  re-arrangement  of  the  atoms  within  a  single 
molecule. 

EXAMPLES. — 1st.  All  synthetical  reactions  belong  to  the  first  class 
of  chemk.il  changes;  as: 

Zn       +        C12         =          ZnCl2 
Zinc.  Chlorine.  Zinc  chloride. 

2d.  All  analytical  reactions  belong  to  the  second  class;  as: 

H2S04         =        H20        4-          S03 
Hydrogen  sulphate.  Water.  Sulphuric  oxide. 

3d.  Substitution  reactions;  as: 

C2H6        -f       C12      =      C2H5C1          +          HC1 
Ethyl  hydride.         Chlorine.         Ethyl  chloride.         Hydrogen  chloride. 
4th.  All  metathetical  reactions  represent  the  fourth  class;  as: 

CaCl2         +        K2(C204)       =       Ca(C204)        +         (KC1)2 
Calcium  chloride.        Potassium  oxalate.       Calcium  oxalate.        Potassium  chloride. 
5th.  The  conversion  of  ammonium  cyanate  into  urea: 

(NH4)(CNO)       =      (CO)(H2N)2 
Ammonium  cyanate.  Urea. 


CHEMICAL  EQUATIONS.  75 

125.  Chemical  Relations  of  Work  and  Energy. — 

In  studying  the  energy-relations  of  matter,  it  is  often  con- 
venient to  consider  the  bodies  concerned  as  forming  mutu- 
ally acting  systems,  whose  parts  at  any  instant  are  definitely 
arranged  with  reference  to  one  another.  Such  a  system  pos- 
sesses energy,  in  part  potential,  due  to  the  relative  position 
of  its  parts,  in  part  kinetic,  due  to  their  motion.  The  action 
of  one  such  system  upon  another  consists  simply  in  the  trans- 
ference of  this  energy  from  one  to  the  other  ;  in  doing  which 
the  one  system  is  said  to  exert  force  upon  the  other.  It  is 
evident,  however,  that  the  amount  of  energy  gained  by  the 
one  system  is  exactly  equal  to  that  which  is  lost  by  the  other. 
So  that  if  we  include  both  systems  in  a  single  larger  system, 
we  see  that  the  total  energy  of  this  larger  system  remains 
unchanged.  Hence  the  total  energy  of  a  material  .system 
can  not  be  changed  in  amount  by  any  action  going  on  within 
the  system ;  although  it  may  be  converted  into  other  forms. 
This  is  the  principle  of  the  Conservation  of  Energy. 

If  an  agent  external  to  the  system  act  upon  it,  however, 
its  action  may  be  either  to  increase  or  to  diminish  the  total 
energy  of  the  system.  Whenever  work  is  done  upon  a  sys- 
tem, its  energy  is  increased ;  arid  w/ienever  the  system  itself 
does  work  upon  other  systems,  its  energy  is  decreased.  The 
amount  of  energy  which  is  stored  up  in  a  system  is  always 
exactly  equal  to  the  amount  of  work  wrhich  is  done  upon  it. 
While  we  can  not  measure  the  total  energy  of  a  system,  we 
can  measure  very  accurately  the  changes  in  energy  which  it 
undergoes.  If  we  suppose  a  definite  system  to  pass  from 
one  definite  state  to  another,  the  energy  lost  or  gained  iu 
the  process  is  evidently  the  difference  between  the  energy 
of  the  system  in  its  initial  and  final  states.  Heat  is  a  form 
of  energy ;  so  that,  if  we  may  assume  that  the  energy  lost 
or  gained  is  heat-energy,  a  measurement  of  the  heat  gained 
or  lost  by  the  system  will  give  us  the  increase  or  decrease  of 
energy  which  the  system  undergoes.  If  a  system  A  whose 


76  THEORETICAL  CHEMTSTHT. 

potential  energy  is  EA  passes  to  a  system  B,  whose  potential 
energy  is  E15,  less  than  EA,  then  the  loss  of  energy  in  the 
process — due  to  a  change  in  the  position  of  the  parts  where- 
by the  stress  between  them  is  diminished — will  evidently  be 
EA — EI5.  This  energy  by  supposition  appears  as  heat;  so  that 
we  may  write  EA— EB=H.  To  return  the  system  B  to  its 
original  state  A,  on  the  other  hand,  requires  energy  to  be 
supplied;  whence  the  equation  EA=EB-fH. 

126.  Tliermo-chemical  Laws. — The  fundamental  laws 
of  therm o-chemistry  are  three  in  number  (Berthelot)  : 

I.  The  amount  of  heat  set  free  in  any  chemical  reaction 
whatever  is  a  measure  of  the  total  work,  both  physical  and 
chemical,  accomplished  in  the  reaction. 

II.  Whenever  a  system  of  bodies  undergoes  physical  or 
chemical  changes  capable  of  bringing  it  to  a  new  state  with- 
out producing  any  mechanical  effect  exterior  to  the  system, 
the  amount  of  heat  set  free  or  absorbed  in  these  changes  de- 
pends only  on  the  initial  and  final  states  of  the  system,  and 
is  independent  of  the  nature  or  order  of  the  intermediate 
states. 

III.  Every  chemical  change  which  is  effected  in  a  system 
without  the  aid  of  outside  energy,  tends  to  the  production 
of  that  body  or  system   of  bodies  the  formation  of  which 
evolves  the  maximum  heat. 

EXAMPLES. —  In  thermo-chemical  equations  the  grarn  is  taken  as 
the  unit  of  atomic  mass,  II  representing  one  gram  of  hydrogen  and 
O  sixteen  grams  of  oxygen;  so  that,  calling  a  heat-unit  the  amount 
of  heat  necessary  to  raise  the  temperature  of  one  gram  of  water  one 
degree  (i.  e.,  a  water-gram  degree),  we  may  write  the  synthetical  reac- 
tion for  the  production  of  water-vapor  at  136-5°,  as  follows: 
(H2)2-f-O2—  (H2O)2-f  114,320  water-gram  degrees; 

and  this  by  the  first  law  measures  the  total  work  accomplished  in  the 
reaction.  Again,  when  stannous  oxide  SnO  is  formed  by  the  union 
of  tin  and  oxygen,  73,800  heat-units  are  evolved;  but  if  the  resulting 
product  is  stannic  oxide  SnO2,  145,400  units  are  set  free.  Hence  by 
the  third  law  the  latter  substance  is  always  formed,  in  case  the  oxygen 


CHEMICAL  EQUATIOXS.  77 

is  present  in  excess.  When  one  gram  of  hydrogen  unites  with  eight 
grains  of  oxygen  to  form  water  (liquid),  34,180  heat-units  are  evolved; 
while  if  the  higher  oxide  H.2O2  be  formed,  one  gram  of  hydrogen 
evolves  only  23,500  units  of  heat.  In  this  ease  therefore,  even  in 
presence  of  an  excess  of  oxygen,  it  is  the  lower  oxide  and  not  the 
higher  which  will  be  formed,  according  to  the  third  law. 

Moreover  it  will  be  observed  that  hydrogen  peroxide  H2O2  can  not 
be  formed  from  hydrogen  oxide  H2O  without  the  absorption  of  energy 
from  some  source  outside  the  system  itself.    The  equation  is: 
(H20)2+O2=(H2O2)2— 44,000  water-gram  degrees. 
Reactions  are  classified  thermically  by  Berthelot  as  exothermic  and 
endothermic,  according  as  heat  is  evolved  or  absorbed  during  their 
progress.     Thus  the  reaction  between  hydrogen  and  chlorine  evolves 
heat,  and  is  therefore  an  exothermic  reaction : 

H2+C12=(HC1)2-|-44,000  water-gram  degrees. 

While  when  hydrogen  combines  with  iodine  vapor  heat  is  absorbed 
and  the  reaction  is  endothermic : 

H2-f-I2:={HI)2— 3,060  water-gram  degrees. 

In  accordance  with  the  law  that  the  tendency  of  the  energy  of  a  sys- 
tem is  always  toward  a  minimum,  it  is  found  that  substances  like 
hydrogen  iodide,  hydrogen  peroxide,  cyanogen,  acetylene,  nitrogen 
chloride,  and  the  oxides  of  nitrogen  and  chlorine,  all  of  which  are 
formed  from  their  constituents  with  absorption  of  heat — by  endother- 
mic reactions — are  more  or  less  unstable;  being  either  spontaneously 
decomposable  and  even  explosive,  like  nitrogen  chloride  and  the  chlo- 
rine oxides,  or  readily  undergoing  changes  by  slight  external  causes; 
but  in  all  cases  evolving  heat  by  their  decomposition.  Carbon  di-sul- 
phide,  for  example,  is  an  endothermic  compound;  and  Thorpe  has  re- 
cently shown  that  the  shock  of  mercuric  fulminate  exploded  in  its 
vapor  decomposes  it,  depositing  both  carbon  and  sulphur.  While, 
therefore,  the  formation  of  an  endothermic  substance  can  not  take 
place  without  the  aid  of  outside  energy,  so,  on  the  other  hand,  the 
decomposition  of  an  exothermic  substance  can  not  occur  without  this 
aid.  An  exothermic  compound  is  therefore  stable. 

The  third  law  teaches  us  further  that  if  a  substance  A, 
in  uniting  with  a  given  metal,  produces  more  heat  than  is 
evolved  when  B  unites  with  the  same  metal,  A  will  displace 
B  from  the  combination.  Thus  chlorine  evolves  more  heat 


78  THEORETICAL  CHEMISTRY. 

in  combining  with  the  metals  than  either  bromine  or  iodine 
does.  Hence  it  can  displace  bromine  and  iodine  from  their 
metallic  compounds.  In  general,  whenever  one  metal  dis- 
places another  from  its  state  of  combination,  it  does  so  be- 
cause energy  tends  to  a  minimum,  and  the  production  of  the 
new  compound  is  attended  with  an  increased  evolution  of 
heat. 

127.  Intensity  of  Chemical  Action. —  Helmholtz  re- 
gards each  atom  of  matter  as  charged  with  a  definite  quan- 
tity of  electricity,  these  charges  being  proportional  to  the 
valence  of  the  atoms.  Thus  all  univalent  atoms  have  unit 
charge,  all  bivalent  atoms  a  charge  of  two  units,  all  trivalent 
atoms  a  charge  of  three  units,  and  so  on.  Moreover,  he  con- 
ceives, 1st,  that  the  same  atom  in  different  compounds  can 
be  charged  with  units  of  either  positive  or  of  negative  elec- 
tricity; sulphur,  for  example,  being  in  hydrogen  sulphide  a 
negative  substance,  and  in  sulphurous  oxide  a  positive  one. 
And  2d,  that  their  electrical  charges  are  held  more  strongly 
by  some  atoms  than  by  others ;  an  atom  of  zinc,  for  exam- 
ple, holding  its  positive  charge  more  strongly  than  an  atom 
of  copper  does  its  negative  one.  Further,  an  electrically 
neutral  molecule,  whether  simple  or  compound,  will  have 
each  unit  of  positive  electricity  on  one  of  its  atoms  neutral- 
ized by  an  equal  unit  of  negative  electricity  on  another 
atom.  Since  a  gas  set  free  by  electrolysis  is  neutral,  it  fol- 
lows that  one  atom  positively  charged  combines  with  another 
negatively  charged,  even  when,  as  in  tl\e  case  of  hydrogen,  for 
example,  these  atoms  are  alike ;  thus  agreeing  with  the  infer- 
ence from  the  law  of  Avogadro  that  a  molecule  of  hydrogen 
is  really  composed  of  two  atoms.  Again,  any  atom  or  group 
of  atoms  which  can  be  substituted  for  another  must  have  an 
equal  electrical  charge.  And,  since  every  equivalent  mass 
has  unit  charge,  the  number  of  unit  charges  will  be  equal 
to  the  number  of  equivalent  masses  in  the  atomic  mass ;  i.e., 
will  be  the  valence  of  the  atom. 


STOICHTOMETRICAL  CALCULATIONS.  79 

% 

As  to  the  magnitude  of  these  atomic  charges,  Helmholtz 
calculates  that  they  must  be  enormous.  ' '  The  electricity  of 
one  milligram  of  water,"  he  says,  "  separated  and  communi- 
cated to  two  balls  a  kilometer  distant,  would  produce  an 
attraction  between  them  equal  to  the  weight  of  26,800  kilo- 
grams." Or,  comparing  the  electrical  attraction  between  two 
quantities  of  oxygen  and  hydrogen  with  their  gravitational 
attraction,  he  finds  the  electrical  force  to  be  71,000  billion 
times  greater  than  the  gravitational  force. 

Faraday  long  ago  expressed  his  conviction  that  the  forces 
termed  chemical  affinity  and  electricity  are  one  and  the  same. 
And  now  Helmholtz,  having  proved  by  experiment  that  in 
the  phenomena  of  electrolysis  no  other  force  acts  but  the 
mutual  attractions  of  the  atomic  electric  charges,  comes  to 
the  equivalent  conclusion  "that  the  very  mightiest  among 
the  chemical  forces  are  of  electric  origin." 

§  2.     STOICHIOMETRICAL  CALCULATIONS. 

?28.  Definition. — Stoichiometry  is  that  department  of 
Chemistry  which  considers  the  numerical  relations  of  atoms. 
All  calculations,  therefore,  which  can  be  made  from  the 
atomic  masses  and  volumes  are  stoichiometrical  calculations. 

129.  Calculations  Founded  on  Mass. —  Every  atom 
has  its  own  mass,  called  the  atomic  mass.  The  atomic  mass 
is  the  smallest  mass  of  any  simple  or  elementary  substance — 
referred  to  the  atom  of  hydrogen  as  unity  —  which  takes 
part  in  any  chemical  change. 

A  molecule  being  built  up  of  atoms,  a  molecular  mass  is 
the  sum  of  the  atomic  masses  of  which  it  is  composed.  It 
is  also  equal  to  twice  the  mass  of  a  given  volume  of  a  sub- 
stance in  the  state  of  vapor,  compared  with  the  same  volume 
of  hydrogen. 

If  the  substance  be  not  volatile  and  can  not  be  weighed  in 
the  state  of  gas,  its  molecular  mass  is  that  mass  of  it,  in  its 


80  THEORETICAL  CHEMISTRY. 

'to- 
solid  condition,  which  has  the  same  specific  heat  as  fourteen 
units  of  mass  of  lithium  at  the  same  temperature. 

13O.  Mass  Concerned  in  Chemical  Changes. — Since 
every  chemical  change  is  simply  an  alteration  in  the  position 
and  association  of  atoms,  every  chemical  equation  which  rep- 
resents such  a  change,  represents  it  as  taking  place  between 
definite  quantities  of  matter.  An  equation  expresses  not 
only  the  fact  of  chemical  reaction  between  two  bodies,  but 
also  indicates  the  quantities  of  matter  concerned  in  it. 

EXAMPLES. — S  stands  for  one  atom  of  sulphur,  with  an  atomic 
mass  of  32.  O3  represents  three  atoms,  or  (16x3)  48  parts  of  oxygen. 
SO3  expresses  the  fact  that  one  atom  of  sulphur  (32)  and  three  atoms 
of  oxygen  (48)  have  united  to  form  a  molecule  of  sulphuric  oxide, 
with  a  molecular  mass  of  (48+32)  80.  So  Ca(CO8)  represents  a  mol- 

Ca     C          O, 
ecule  of  calcium  carbonate,  with  a  molecular  mass  of  40-{-12  +  (]6x3) 

K     N     O3 
=100.     The  molecular  mass  of  K(NO3)  is  39+14+48— 101. 

So  the  equation 

Pb"(NO3)2+Na2(SO4)=Pb"(S04)4-(NaNO.{)2 

— one  molecule  of  lead  nitrate  and  one  of  sodium  sulphate,  yield  one 
molecule  of  lead  sulphate  and  two  of  sodium  nitrate— may  be  read 
by  mass  thus: 

207  f  (14+48)2     +    (23X2)f32f&4    =    207+ (32 1 64)    +    (23+14+48)2 
Pb"(N03)2     +     Na.2(S04)     =     Pb"(S04)    +    (NaN03), 

331  -{-  142  303         +          170 

Three  hundred  and  thirty-one  parts  of  lead  nitrate  and  one  hun- 
dred and  forty-two  parts  of  sodium  sulphate  yield  three  hundred  and 
three  parts  of  lead  sulphate  and  one  hundred  and  seventy  parts  of 
sodium  nitrate. 

(For  convenience  of  calculation  in  the  examples  and  exercises  whole 
numbers  will  generally  be  taken  to  represent  the  atomic  and  molecu- 
lar masses.) 

131.  Calculation  of  Percentage  Composition. — Know- 
ing the  molecular  mass  of  any  substance,  the  number  of  atoms 
which  it  contains,  and  the  atomic  mass  of  each,  it  is  easy  to 
calculate  its  percentage  composition ;  i.  e. ,  its  composition  in 


ST01CHIOMKTIUCAI.   CALC  I  LATWXS.  81 

100  parts  —  the  form  in  which  the  results  of  analysis  are  usu- 
ally given. 

Representing  the  molecular  mass  by  222,  the  atomic  mass 
of  any  constituent  by  a,  the  number  of  atoms  of  that  con- 
stituent by  22,  and  its  percentage  amount  by  jf,  then  we  have 
evidently  the  proportion  : 

222  :  an  :  :  100  :  ;x; 
whence  the  formula  : 

£22  x  100 

x=~vr        w 

To  find,  therefore,  the  percentage  amount  of  any  constit- 
uent in  a  molecule,  we  have  the  following  rule  : 

Multiply  the  atomic  mass  by  the  number  of  atoms 
and  this  product  by  1OO.  Divide  the  final  product  by 
the  molecular  mass,  and  the  quotient  will  be  the  per- 
centage amount  of  that  constituent. 

By  repeating  this  process  for  each  atomic  constituent,  the 
percentage  composition  of  the  molecule  may  be  obtained. 

EXAMPLES.  —  What  is  the  percentage  composition  of  calcium  sul- 
phate, Ca(SO4)  ? 

By  the  formula,  the  molecule  contains  of 

Calcium,  one  atom  (at.  ms.  40)  ......     40 

Sulphur,  one  atom  (at.  ms.  32)  ......     32 

Oxygen,  four  atoms  (at.  ms.  16)  .....      64 

Molecular  mass  of  calcium  sulphate,  136 
Substituting  in  the  percentage  formula,  the  quantity  of 


Calcium  in  100  parts  is  _    29-41 

136 

32X100 

Sulphur      «       »       «  -=    23-53 

136 


Oxygen       "       <<       "  _    47<M 

136 

100-00 


82  THEOliKTK  'A  L  (  'HKM1HTH  Y. 

132.  Other  Problems  by  this  Formula.—  In  the  for- 
mula given  above  (1),  the  four  quantities  a,,  22,  222,  and  x 
are  employed.  Any  three  of  them  being  known,  of  course 
the  fourth  can  be  found.  There  are  therefore  three  more 
cases  to  be  here  considered. 

SECOND  CASE.  —  Having  the  percentage  amount  of  any 
constituent,  its  atomic  mass,  and  the  molecular  mass  of  the 
compound  given,  to  find  the  number  of  atoms  of  that  con- 
stituent in  the  molecule. 

By  transposition,  formula  (1)  gives  : 


whence  we  derive  the  following  rule  : 

Multiply  the  molecular  mass  by  the  percentage 
amount  of  the  given  constituent,  and  divide  the  prod- 
uct by  its  atomic  mass,  multiplied  by  1OO.  The  quo- 
tient is  the  number  of  atoms  of  that  constituent  in  the 
molecule. 

Having  obtained  in  this  way  the  number  of  each  kind 
of  atoms  composing  a  molecule,  it  is  easy  to  construct  the 
molecular  formula. 

EXAMPLES.  —  What  is  the  formula  of  quartz,  its  molecular  mass 
being  60,  and  its  percentage  composition: 

Silicon  ................     46-67 

Oxygen  ...............     53-33 

100-00 

The  atomic  mass  of  silicon  is  28;  hence  by  formula  (2)  the  number 
of  atoms  of  -  £' 

Q-T  n  >.    60X46-67 

Silicon  would  be  -  =  1 
100X28 

60X53-33 

Oxygen      "        "    -  —  =2 

100X16 

The  molecular  formula  of  quartz  is  therefore  SiO.,. 


STOH'HIOMKTRH'AL  CALCULA  T1ONS.  83 

THIRD  CASE.  —  Having  the  percentage  composition,  the 
number  of  atoms  of  any  constituent  in  the  molecule,  and 
the  molecular  mass,  to  find  the  atomic  mass  of  that  atomic 
constituent.  From  formula  (1)  by  transposition,  we  obtain  : 


The  rule  therefore  is  : 

Multiply  the  molecular  mass  by  the  percentage 
amount  of  the  constituent  whose  atomic  mass  is  de- 
sired, and  divide  the  product  by  the  number  of  atoms 
multiplied  by  1OO.  The  quotient  is  the  atomic  mass 
required. 

EXAMPLES.  —  The  molecular  mass  of  silver  nitrate  is  170;  it  con- 
tains 63-53  per  cent  of  silver,  and  has  but  one  atom  of  silver  in  a 
molecule.  What  is  the  atomic  mass  of  silver? 

Making  the  necessary  substitutions  in  formula  (3)  we  have 

170X63-53 

-  =108 
100X1 

Hence  the  atomic  mass  of  silver  is  108. 

FOURTH  CASE.  —  Having  the  atomic  mass  of  any  constitu- 
ent, the  number  of  atoms  of  it  in  the  molecule,  and  its  per- 
centage amount,  to  find  the  molecular  mass. 

By  a  final  transposition  of  formula  (1),  we  obtain  : 


Whence  the  rule  : 

Multiply  the  atomic  mass  of  the  constituent  given 
by  the  number  of  its  atoms,  and  this  product  by  1OO. 
Divide  the  final  product  by  the  percentage  amount 
of  that  constituent,  and  the  quotient  is  the  molecular 
mass. 

EXAMPLES.  —  Salt  contains  39-32  per  cent  of  sodium,  whose  atomic 
mass  is  23.  In  a  molecule  of  salt  there  is  but  one  atom  of  sodium. 
What  is  the  molecular  mass  of  salt? 


84  THEORETICAL  CHEMISTRY. 

23V1  VlOO 
By  substitution,  —  —  =  58-5.     The  molecular  muss  of  salt 

is  therefore  58-5. 

Again,  ferric  oxide  contains  three  atoms  of  oxygen,  or  30  per  cent. 
What  is  its  molecular  mass  ? 


By  the  formula,  -  =  160,  the  molecular  mass. 

133.  Calculation  of  an  Atomic  Group.  —  Iii  some 
cases  it  is  desirable  to  calculate  the  percentage  amount  of  a 
group  of  atoms  in  any  molecule.  Formula  (1)  above  given 
enables  us  to  do  this,  using  a  to  indicate  the  mass  of  the 
group,  and  n  the  number  of  such  groups  in  the  molecule. 

EXAMPLES.  —  Ammonium  nitrate,  (NH4)NO3,  breaks  up  under  the 
influence  of  heat  into  one  molecule  of  nitrogen  oxide,  N2O,  and  two 
molecules  of  water,  (H2O)2.  How  much  nitrogen  oxide  in  100  parts 
of  ammonium  nitrate? 


,,  44x1X100 

By  formula  (1)  -  ,  we  have  ---  =  55.     Hence  am- 

monium nitrate  yields  55  per  cent  of  nitrogen  oxide. 

134.  Other  than  Percentage  Numbers.  —  Problems 
often  arise  which  require  the  quantity  of  a  constituent  in 
less  or  more  than  100  parts.  The  answers  to  such  problems 
can  of  course  be  obtained  by  stating  the  proportion  for  each 
problem;  but  they  may  be  derived  also  from  formula  (1) 
already  given,  by  putting  y  —  the  quantity  of  the  constitu- 
ent —  in  place  of  x,  and  z  —  the  quantity  of  the  compound  — 
in  place  of  100.  The  formula  then  becomes  : 

anxz         (5) 

222 

Whence  the  rule  :   - 

Multiply  the  mass  of  the  constituent  contained  in 
one  molecule  by  the  mass  of  the  compound  given  in 
the  problem,  and  divide  this  product  by  the  molecular 
mass.  The  quotient  is  the  quantity  of  the  constituent 
required, 


STOICHIOMETRICAL  CALCULATIONS.  85 

EXAMPLES.  —  How  much  iodine  may  be  obtained  from  236  grams 
of  potassium  iodide,  the  atomic  mass  of  iodine  being  127,  and  the 
molecular  mass  of  potassium  iodide  being  166? 

By  proportion.  As  166  parts  of  potassium  iodide  give  127  of  iodine, 
it  is  obvious  that  the  quantity  given  by  236  parts  would  be  given  by 
the  proportion  166  :  236  :  :  127  :  y.  Whence  jr=180-5.  Answer,  180-5 
grams  iodine. 

By  formula  (5).     Substituting  for  an  in  formula  (5),  127,  for  z,  236, 

127X236 
and  for  122,  166,  we  have  jr—  -  —  180-5.     Hence  236  grams 

potassium  iodide  yield  180-5  grams  iodine. 

Conversely,  if  the  quantity  of  the  compound  necessary  to 
yield  a  given  mass  of  the  constituent  be  required,  we  obtain 
by  transposition  : 


an 

EXAMPLES.  —  How  much  potassium  iodide  would  be  required  to 
yield  78  grams  iodine? 

1  AA\/  7Q 

Substituting  in  formula  (6)  we  have  z  =  --  =  102.  Answer, 
102  grams  potassium  iodide. 

By  analysis.     If  166  parts  potassium  iodide  yield  127  of  iodine,  to 

166 
yield  1  part  of  iodine  —  -  of  one  part  will  be  required;  and  to  yield 

166       166x78 
78  parts,  78  times  —  or  -  ,  will  be  required.     But  this  is  the 

precise  result  given  above. 

135.  Calculation  from  Equations.  —  The  same  princi- 
ples are  applied  in  calculating  the  mass  of  substances  enter- 
ing into,  or  issuing  from,  chemical  reactions.  The  reaction 
is  first  to  be  expressed  in  the  form  of  an  equation.  The 
molecular  mass  of  all  the  substances  given  are  then  to  be 
written  below  their  respective  formulas.  Having  now  the 
data,  the  problems  are  to  be  solved  by  making  the  following 
proportion  : 

As  the  molecular  mass  of  the  substance  given  is  to 

7 


86  THEORETICAL  CHEMISTRY. 

the  quantity  of  it  given  in  the  problem,  so  is  the  molec- 
ular mass  of  the  substance  required  to  the  quantity 
of  it  required. 

Representing  by  M  the  molecular  mass  of  the  substance 
given,  by  W  the  absolute  mass  of  this  substance  given  in 
the  problem,  by  122  the  molecular  mass  of  the  substance  re- 
quired, and  by  w  the  absolute  mass  of  this  substance,  then 
by  the  above  rule  we  have  the  proportion  M  :  W:  :  222  :  W, 
from  which  the  four  following  formulas  may  be  derived  : 


W  -Z22 


W  M. 

Hence,  any  three  of  these  quantities  being  given,  it  is  easy 
to  find  the  fourth.     Four  cases  thus  arise,  viz  : 

1.  Having  the  absolute  quantity  of  a  factor  and  the  quan- 
tity of  the  product  yielded  by  it,  as  well  as  the  molecular 
mass  of  the  product  ;  to  find  the  molecular  mass  of  the  factor. 

2.  Having  the  molecular  mass  of  both  factor  and  product, 
to  find  the  quantity  of  the  factor  necessary  to  yield  a  given 
mass  of  the  product. 

3.  Having  the  quantity  of  the  factor,  the  quantity  of  the 
product,  and  the  molecular  mass  of  the  factor;  to  find  the 
molecular  mass  of  the  product. 

4.  Having  the  molecular  mass  of  both  factor  and  product, 
to  find  the  mass  of  the  product  from  a  given  weight  of  the 
factor. 

EXAMPLES.  —  Nitric  acid  is  prepared  by  the  action  of  sulphuric 
acid  upon  potassium  nitrate,  according  to  the  following  equation  : 

K(N03)  +  H2(SO4)  =  H(N03)  +  HK(SO4) 

101      -f       98       =       63       +       136 

Problem  1st.  —  125  grams  of  niter  yield  77-97  grains  of  nitric  acid, 
whose  molecular  mass  is  63  ;  what  is  the  molecular  mass  of  potassium 
nitrate  ? 


STOICHIOMETRICAL  CALCULATIONS.  87 

In  this  problem,  122  equals  63,  W  equals  125,  and  w  equals  77-97; 

63X125 

hence  M  =  —        ~  =  101.  Answer. 
77-97 

Problem  2d. — The  molecular  mass  of  niter  is  101,  and  that  of  nitric 
acid  is  63;  how  much  niter  would  be  required  to  yield  77-97  grams 
nitric  acid? 

Here,  the  quantities  being  represented  as  before,  we  have  W  = 

101X77-97 

=  125  grams,  Answer. 

Problem  3d.— 125  grams  of  niter  yield  77-97  grams  of  nitric  acid. 
The  molecular  mass  of  niter  is  101 ;  what  is  the  molecular  mass  of 
nitric  acid? 

101X77-97 

In  this  problem,  m  = =  63,  Answer. 

125 

Problem  4th.— The  molecular  mass  of  niter  is  101  and  that  of  nitric 
acid  is  63;  how  much  nitric  acid  would  125  grams  of  niter  yield? 

63X125 
We  have  w= =  77-97  grams,  Answer. 

Formulas  (2)  and  (4)  are  the  ones  usually  employed,  since 
molecular  masses  may  generally  be  obtained  more  readily  in 
other  ways.  These  two  formulas  may  be  applied  to  a  great 
variety  of  problems,  as  the  following  examples  show. 

EXAMPLES. — Taking  the  equation  for  the  production  of  nitric  acid 
by  the  action  of  su-lphuric  acid  on  potassium  nitrate,  above  given,  the 
following  problems  may  be  worked  by  formula  (2) : 

Problem  1st. — How  much  niter  is  necessary  to  yield  36  grams  of 
nitric  acid? 

101X36 

W=—        — — 57-7  grams,  Answer. 
63 

Problem  2d. — How  much  sulphuric  acid  will  be  required? 

98X36 

Here  M—  98;  hence  W=  —      —  =  66  grams,  Answrer. 

63 

Problem  3rf.  —  How  much  hydro-potassium  sulphate  will  be  pro- 
duced ? 

136X36 

M  in  this  problem  =  136;  hence  W=  —        —  —  77-7  grams,  An- 

63 

swer. 

And  these  problems  by  formula  (4): 


88  THEORETICAL  CHEMISTRY. 

Problem  1st. — How  much  nitric  acid  may  be  produced  i'rom  500 
grams  of  potassium  nitrate? 

222  W       63X500 

W= —  — -    —  =  31T88  trains,  Answer. 

M  101 

Problem  2d. — How  much  sulphuric  acid  would  be  required  to  de- 
compose 500  grams  niter  ? 

98X^00 
Here  m  =  98;  hence  w  — =  485-15  grams,  Answer. 

Problem  M. —  How  much  hydro -potassium  sulphate  would  be 
yielded  by  the  decomposition  of  500  grams  of  potassium  nitrate  by 
sulphuric  acid? 

136X500. 

In  this  problem  m  =  136;  hence  w  = —  673-27  grains. 

In  all  the  above  problems  it  has  been  assumed  that  cadi 
molecule  of  the  factor  yielded  one  of  the  product.  If  in  any 
reaction  this  is  not  true,  then  M  and  222  must  represent  the 
sum  of  the  molecular  masses  expressed  in  the  equation. 

136.  Volume  Calculations  from  Equations. — Every 
molecular  formula  represents  two  volumes.  Hence  any  equa- 
tion composed  of  such  formulas  may  be  read  by  volume. 
From  these  volumes  calculations  may  be  made  as  well  as 
from  the  masses. 

EXAMPLES. — In  the  equation : 

(C0)2  +  02  =  (C02)2 

— two  molecules  carbon  mon-oxide  and  one  molecule  of  oxygen  yield 
two  molecules  carbon  di-oxide  — the  volume  relations  may  be  read 
thus:  four  volumes  carbon  mon-oxide  and  two  volumes  of  oxygen 
give  four  volumes  of  carbon  di-oxide.  From  these  relations  the  fol- 
lowing problems  may  arise: 

Problem  1st. — How  much  carbon  di-oxide  is  formed  by  the  com- 
bustion of  1  liter  of  carbon  mon-oxide  ? 

As  4  volumes  carbon  mon-oxide  yield  4  of  carbon  di-oxide,  1  vol- 
ume will  yield  1  volume,  and  1  liter  of  course  1  liter,  Answer. 

Problem  Id. — How  much  oxygen  is  needed  to  convert  2  liters  car- 
bon mon-oxide  to  carbon  di-oxide? 

Four  volumes  by  the  equation  require  2  of  oxygen ;  hence  2  liters 
will  require  1  liter  of  oxygen,  Answer, 


STOICHIOMETRICAL  CALCULATIONS.  89 

Problem  M. — To  form  100  cubic  centimeters  of  carbon  di-oxide 
how  much  carbon  mon-oxide  must  be  burned? 

Four  volumes  carbon  di-oxide  require  the  combustion  of  four  of 
carbon  mon-oxide;  100  cubic  centimeters  will  require  its  own  volume 
therefore,  or  100  cubic  centimeters,  Answer. 

137.  Relations  of  Mass  to  Volume. — It  is  often  neces- 
sary to  calculate  the  volume  occupied  by  a  given  mass  of  any 
gas,  or  the  mass  of  any  given  volume.     The  following  are 
the  rules : 

1.  To  determine  the  volume  of  any  gas,  its  mass  being 
given :  Divide  the  mass  of  the  gas  given,  by  the  mass 
of  one  liter ;  the  quotient  is  the  number  of  liters. 

2.  To  determine  the  mass  of  any  given  volume  of  gas : 
Multiply  the  number  of  liters  of  gas  by  the  mass  of 
one  liter ;  the  product  is  the  mass  of  the  given  volume. 

EXAMPLES. 

1.  What  volume  is  occupied  by  6-08  grams  of  oxygen  gas? 

The  mass  of  one  liter  of  oxygen  is  1-43  grams;  hence  in  6-08 
grams  there  will  be  as  many  liters  as  1-43  is  contained  times  in  6-08; 
or  4-25  liters,  Answer. 

2.  What  is  the  mass  of  25  liters  of  nitrogen  gas  ? 

The  mass  of  one  liter  of  nitrogen  gas  is  1-26  grams.  1-26X25  =• 
31-5;  hence  the  mass  of  25  liters  of  nitrogen  is  31-5  grams,  Answer. 

138.  Relation  of  Volume  to  Density. — Relative  den- 
sity being  the  mass  of  one  volume  of  any  gas  —  compared 
with  the  same  volume  of  hydrogen  —  and  molecular  mass 
being  the  mass  of  two  volumes,  it  is  evident  that  the  relative 
density  of  any  body  in  the  state  of  gas  may  be  obtained  by 
dividing  its  molecular  mass  by  two. 

Having  the  relative  density  of  any  gas — which  expresses 
how  many  times  the  gas  is  denser  than  hydrogen — the  mass 
of  one  liter  may  be  readily  obtained  by  multiplying  it  into 
the  mass  of  one  liter  of  hydrogen.  The  mass  of  one  liter 
of  hydrogen  is  0*0896  grams,  or  1  crith. 


92  THEORETICAL  CHEMISTRY. 

lowered,  the  formula  for  calculating  an  increase  of  volume 
will  be  approximately : 

V  =  Vx(l+  -003665 1)  (1) 

And  by  transposing,  the  formula  by  which  the  volume  at  a 
lower  temperature  can  be  calculated  is  obtained : 

V 

V=  (2) 

(1  +  -003665 1) 

EXAMPLES. 

1.  A  gas  measures  15  cubic  centimeters  at  0°;  what  will  it  measure 
at  60°? 

Substituting  in  (1),  V'=  15X(1  +  60X'U03665)  =  18-298  c.  c.,  Ans. 

2.  What  will  a  gas  measure  at  0°,  which,  at  100°,  measures  40-1  c. c.? 

40-1 

Substituting  in  (2),  V—  —  =  29-345  c.  c.,  Answer. 

(I  +  IOOX'003665) 

3.  A  gas  measures  560  c.  c.  at  15°;  what  will  it  measure  at  95°? 

/  ( 1 -I- 95  X '003665) 

Here  t  =  15°  and  f  '  =  95°.      Hence  V  =  560  - 

(1-J-16X '008666) 

715-6  cubic  centimeters,  Answer. 


EXERCISES.  93 


EXERCISES. 
§1. 

1.  What  is  molecular  stability? 

2.  What  is  a  chemical  reaction?     A  chemical  re-agent? 

3.  Explain  why  mass-reactions  may  be  accurately  represented  by 
molecular  formulas. 

4.  What  is  a  chemical  equation?     How  is  it  constructed? 

5.  Give  the  rule  for  writing  equations.     Illustrate  it. 

6.  Does  matter  disappear  in  chemical  changes? 

7.  How  are  chemical  reactions  classified  ?     Illustrate. 

8.  Why  does  solution  favor  chemical  changes? 

9.  Give  Berthollet's  first  law.     Define  precipitate,  precipitation. 

10.  Distinguish  the  chemical  part  of  this  process  of  precipitation 
from  the  physical. 

11.  Give  Berthollet's  second  law.     Illustrate  it. 

12.  How  may  results  be  predicted  by  these  laws? 

13.  If  barium  chloride  and  magnesium  sulphate  bo  mixed,  together 
in  solution,  will  there  be  a  reaction?     Lead  nitrate  and  ammonium 
phosphate?     Sodium  hydrate  and  zinc  iodide?     Write  the  reaction 
in  each  case. 

14.  In  what  ways  may  chemical  changes   in   matter  take  place? 
Write  a  reaction  of  each  kind. 

15.  State  the  principle  of  the  Conservation  of  Energy.     How  may 
the  energy  of  a  system  be  varied? 

16.  Give  the  laws  of  Thermo-chemistry.     What  is  an  exothermic 
reaction?    Why  are  substances  formed  by  endothermic  reactions  less 
stable  than  those  formed  by  exothermic  reactions  ? 

§2. 

17.  What  are  stoichiometrical  calculations? 

18.  What  does  a  chemical  equation  represent  by  mass? 

19.  Bead  the  following  equation  by  mass: 

Sr(NOs)a+HNa2P04=HSrP04+(NaNOs)a 

20.  Deduce  the  formula  for  calculating  the  percentage  composition. 
Give  the  rule. 


94  THEORETICAL  C 


21.  What  is  the  percentage   composition  of  potassium  chlorate? 
Of  sodium  carbonate?     Of  K3PO4?     Of  Zn.2SiO4? 

22.  Derive  the  formula,  and  give  the  rule  for  finding  the  number 
of  atoms  of  any  constituent  in  any  molecule. 

23.  Alumina  is  composed  as  follows:    Aluminum  53-50,  Oxygen 
46-50  =  100.     Its  molecular  mass  is  103;  what  is  its  formula? 

24.  The  mineral  wollastonite  has  the  following  composition:  Sili- 
con 24-14,  Calcium  34-48,  Oxygen  41-38  =  100.     Its  molecular  mass  is 
116;  what  is  its  formula? 

25.  How  is  the  formula  forgetting  the  atomic  mass  derived?    Give 
the  rule. 

26.  Tin  oxide  has  a  molecular  mass  of  150;  it  contains  one  atom 
of  tin,  or  78-67  per  cent.    What  is  the  atomic  mass  of  tin? 

27.  Magnetic  iron  oxide  contains  three  atoms  of  iron;  its  percent- 
age amount  of  oxygen  is  27-60,  and  its  molecular  mass  is  232.    What 
is  the  atomic  mass  of  iron? 

28.  What  is  the  formula  and  what  the  rule  for  finding  the  molecu- 
lar mass? 

29.  Zinc  sulphide  contains  67  per  cent  of  zinc,  or  one  .atom  ;   the 
atomic  mass  of  zinc  is  65;  what  is  the  molecular  mass  of  zinc  sulphide? 

30.  How  may  the  atomic  groupings  into  which  a  molecule  can  be 
broken  up  be  calculated  ? 

31.  The   mineral  magnesite,  MgCO3,  is  decomposed  by  heat  into 
MgO  and  CO2  ;  what  are  the  percentage  amounts  of  these  substances 
which  it  contains? 

32.  Give  the  formula  and  rule  in  cases  where  other  than  percentage 
numbers  are  required. 

33.  How  much  lead  may  be  obtained  from  564  kilograms  lead  sul- 
phide?    (At.  ms.  lead,  207;  mol.  ms.  lead  sulphide,  239.) 

34.  How  much  calcium  phosphate  is  required  to  give  356  kilograms 
phosphorus?     (At.  ms.  of  phosphorus  is  31;  the  molecular  mass  of 
calcium  phosphate  is  310.) 

35.  How  may  the  products  of  a  reaction  be  calculated  from  the 
factors  ?     Give  the  rule. 

36.  Derive  the  four  formulas  given,  and  show  the  class  of  problems 
to  which  each  applies. 

37.  From  the  following  equation: 

Zn(NO3)2+K2CO3=ZnCO3+(KNO3)2 

calculate  the  quantity  of  zinc  nitrate  required  to  give  103-17  grams 
zinc  carbonate. 


KXKHCISES.  95 

38.  How  much  ZnCO3  may  be  obtained  from  156  grams  Zn(NO3)2? 

39.  How  much  K2CO3  is  needed  to  decompose  75  grams  Zn(NO3)2? 

40.  What  quantity  of  potassium  nitrate  will  result? 

41.  How  much  potassium  carbonate  must  bo  used  in  order  to  obtain 
54  grams  zinc  carbonate? 

42.  How  much  potassium  nitrate  will  be  produced? 

43.  156  grams  zinc  nitrate  yield  103-17  grams  zinc  carbonate  (mol. 
ms.  125);  what  is  the  molecular  mass  of  zinc  nitrate? 

44.  103-17  grams  zinc  carbonate  are  obtained  from  156  grams  of 
zinc  nitrate  (mol.  ms.  189);  what  is  the  molecular  mass  of  zinc  car- 
bonate ? 

45.  Read  the  following  equation  by  volume: 

CH4+(02)2=C02+(H20)2 

46.  How  much  oxygen  is  needed  to  burn  1  liter  of  CH4? 

47.  What  volume  of  carbonic  di-oxide  is  produced? 

48.  How  much  CH4  is  needed  to  give  1  cubic  meter  of  steam? 

49.  What  volume  does  a  kilogram  of  oxygen  occupy? 

50.  One  liter  of  CH4  in  burning  gives  what  mass  of  CO2? 

51.  Calculate  the  mass  of  one  liter  of  chlorine;  of  phosphorus;  of 
H2S;  of  00;  of  PC13;  of  HNO3. 

52.  Calculate  the  specific  gravity  of  nitrogen. 

53.  The  specific  gravity  of  hydrogen  iodide  is  4-43;    what  is  its 
molecular  mass  ? 

54.  How  is  the  formula  for  reducing  gaseous  volumes  to  the  normal 
pressure  deduced  ?     Give  the  rule. 

55.  What  is  the  normal  volume  of  a  liter  of  oxygen  measured  at 
756mm.?     At  795?     At  1140?     At  380? 

56.  What  volume  would  350  c.  c.  of  ammonia-gas,  measured  at  74°, 
have  at  0°?     At  100°?     At  20°? 


PART  SECOND. 


INORGANIC  CHEMISTRY. 


(97) 


Part  Second. 
INORGANIC  CHEMISTRY. 


CHAPTER  FIRST. 

HYDROGEN. 

Symbol  H.  Atomic  Mass  1.  Valence  I.  Relative  Density  1. 
Molecular  Mass  2.  Molecular  Volume  2.  T/ie  Jlfoss  of  one 
liter  at  0°  is  0-089578  gram  (1  mtfi). 

142.  History. — Hydrogen  was  apparently  known  to  Par- 
acelsus in  the  16th  century.  It  was  first  accurately  de- 
scribed by  Cavendish  in  1766,  who  called  it  inflammable 
air.  Lavoisier  gave  it  the  name  hydrogen. 

14*?.  Occurrence.  —  Hydrogen  occurs  free  in  certain 
volcanic  gases ;  Bunsen  found  that  it  formed  45  per  cent 
of  the  gaseous  exhalations  of  Nimarfjall,  Iceland.  It  also 
occurs  in  the  gases  accompanying  petroleum.  It  is  shown 
by  the  spectroscope  to  exist  in  the  sun,  the  fixed  stars,  and 
in  some  of  the  nebulas.  Graham  obtained  from  the  Lenarto 
meteorite — a  remarkably  pure  iron — three  times  its  own  vol- 
ume of  this  gas. 

Combined,  hydrogen  exists  in  water,  every  cubic  centi- 
meter of  which  contains  1J  liters ;    also  in  petroleum  and 
bitumen,  and  in  all  animal  and  vegetable  tissues. 
•    144.  Preparation. — Simple  molecules  are  obtained  from 

(99) 


100  INORGANIC  CHEMISTRY. 

compound  molecules  by  re-arranging  their  atoms.     For  the 
production  of  hydrogen  this  re-arraugemeut  may  be  effected : 

I.  By  the  action  of  some  physical  agent ;  as 

(a)  Heat. — When  melted  platinum  is  dropped  into  water, 
both  hydrogen  and  oxygen  gases  are  evolved : 

H— O— H  H     O    H 

forming     |       1 1 
H— O— H  H    O    H 

or: 

(H20)2  =  <H2)2  +  02 

This  process  is  called  dissociation. 

(b)  Electricity.  —  In   the    electrolysis    of    hydrogen   com- 
pounds (p.  139). 

II.  By  superior  chemical  attraction;  as  in  the  action  of 
sodium  upon  water  at  ordinary  temperatures : 

(HP),     +     Na,     =     (HNaO),     +      H2 

Hydrogen  oxide.         Sodium.  Sodium  hydrate.          Hydrogen. 

or  of  iron  and  other  metals,  at  a  red  heat : 

(H.O),   +    Fe6  =  (Fe,0,),   +    (H,), 

Water.  Iron.  Iron  oxide.  Hydrogen. 

Or  of  zinc  upon  an  acid,  as  sulphuric  acid  : 

H2(S04)     +     Zn     =    Zn(S04)     +     H, 

Hydrogen  sulphate.         Zinc.  Zinc  sulphate.  Hydrogen. 

or  of  magnesium  upon  a  base,  as  potassic  base  : 

(HKO),     +     Mg    =    Mg"(OK)2     +     H2 

Potassium  hydrate.     Magnesium.      Potassio-magnesium        Hydrogen. 

oxide. 

EXPERIMENTS. — The  apparatus  by  which  hydrogen  is  obtained  by 
the  action  of  sodium  upon  water  is  shown  in  Fig.  1.  It  consists  of  a 
glass  cylinder  filled  with  water,  and  inverted  in  water  contained  in 
a  cistern.  Upon  throwing  a  fragment  of  sodium  upon  the  water,  it 
rolls  about  upon  the  surface,  with  a  hissing  noise,  as  a  silver-white 
globule.  By  means  of  the  wire-gauze  cage  shown  in  the  figure,  this 
globule  may  be  depressed  below  the  surface,  and  held  beneath  the 


PROPERTIES  OF  HYDROGEN. 


101 


mouth  of  the  glass  cylinder.    The  hydrogen  gas  set  free  by  the  action 
of  the  sodium,  rises  in  bubbles  into  the  cylinder,  displacing  the  water. 

By  repeating  the  process  a 
sufficient  number  of  times, 
the  cylinder  may  be  filled. 

The  usual  method  of  pre- 
paring hydrogen  is  by  the 
action  of  zinc  upon  sulphu- 
ric acid,  for  which  an  appa- 
ratus similar  to  that  shown 
in  Fig.  2  may  be  used.  The 
zinc  is  placed  in  the  two- 
Fig,  i.  Preparation  of  Hydrogen  by  Sodium,  necked  bottle  — in  place  of 

which  a  wide-mouthed  bot- 
tle having  two  holes  through  the  cork,  may  be  substituted;  through 
one  of  these  openings  a  funnel-tube  passes  to  the  bottom  of  the  bottle, 
and  through  the  other  a  delivery-tube  passes  to  the  water-cistern, 
terminating  beneath  an  inverted  cylinder  filled  with  water,  which 
stands  within  it.  On  pouring  diluted  sulphuric  acid  —  one  part  of. 
the  commercial  acid  mixed  with  four  parts  of  water  and  cooled  — 
through  the  funnel -tube  upon 
the  zinc,  effervescence  takes 
place  and  bubbles  escape  from 
the  delivery-tube.  After  allow- 
ing time  for  the  air  in  the  bot- 
tle to  escape,  the  gas  may  be 
collected  for  use. 

145.   Properties. — I. 

PHYSICAL. — Hydrogen  is  a 
colorless,  odorless,  and  taste- 
less gas.  It  is  the  lightest 
form  oljrmatter  known,  be- 
ing 14*43  times  lighter  than 
air,  11,000  times  lighter  than  water,  and  240,000  times  lighter 
than  platinum.  Its  molecular  mass  is  therefore  smaller  than 
that  of  any  other  substance.  For  this  reason,  as  shown  in 
the  section  on  diffusion,  its  diffusibility  is  higher  than  that 
of  any  other  gas.  Its  refractive  power  on  light  is  remark- 

8 


Fig.  2.   Preparation  of  Hydrogen  from 
Zinc  and  Sulphuric  Acid. 


102  INORGANIC  CHEMISTRY. 

able,  being  6*614  times  that  of  air.  It  is  soluble  to  a  very 
slight  extent  in  water,  100  volumes  of  which  dissolve  but 
1*9  of  hydrogen. 

When  subjected  to  a  pressure  of  160  atmospheres,  and 
cooled  in  boiling  nitrogen  to  — 213°,  Olzewski  obtained  it 
as  a  colorless  and  transparent  liquid  running  down  the  walls 
of  the  tube,  by  allowing  the  gas  suddenly  to  expand  to  40  at- 
mospheres ;  this  sudden  expansion  producing  increased  cold. 
Its  critical  temperature  and  pressure  have  not  therefore  been 
determined  experimentally.  The  former,  however,  has  been 
calculated  as  — 240°  and  the  latter  as  13 '3  atmospheres. 

Owing  to  its  lightness,  the  velocity  of  sound  in  hydrogen 
is  trebled,  but  its  intensity  is  much  enfeebled.  Hydrogen 
is  the  standard  of  relative  density,  and  of  molecular  mass 
and  volume.  The  mass  of  1  liter  at  0°  and  760  millimeters 
is  -089578  gram,  or  1  crith. 

EXPERIMENTS. — The  rapid  diffusion  of  hydrogen  gas  may  be  shown 
very  well  by'the  apparatus  represented  in  Fig.  3.  A  light,  unglazed, 
cylindrical  cup  of  earthen-ware  —  such  as 
is  used  in  voltaic  batteries — is  cemented,  at 
its  open  end,  to  a  glass  funnel  whose  stem 
is  prolonged  by  a  slender  tube,  which  dips 
into  colored  water.  The  whole  may  be  sup- 
ported on  any  convenient  stand.  If  now, 
a  bell-glass  filled  with  hydrogen  be  brought 
over  this  earthen  cup,  the  gas  diffuses  so 
much  more  rapidly  into  the  cylinder  than 
the  air  diffuses  out,  that  an  increase  of  vol- 
ume takes  place  within  it  and  the  gas  bub- 
bles out  violently  through  the  water.  When 
the  bell-glass  is  removed,  the  hydrogen 
within  the  cylinder  being  now  in  excess, 
diffuses  so  rapidly  outward  as  to  produce 

a  partial  vacuum,  so  that  the  colored  water 
Fig.  3.   Diffusion  Apparatus.     . r     ,    ,„  •     ^     <.   •> 

rises  half  a  meter  or  more  in  the  tube. 

The  levity  of  hydrogen  may  be  shown  by  using  the  gas  to  inflate 
soap-bubbles.  When  detached  from  the  pipe,  they  rise  rapidly.  Any 


PROPERTIES  OF  HYDROGEN. 


103 


bag  made  of  thin  tissue,  such  as  collodion  or  varnished  paper,  may 
be  filled  with  hydrogen,  and  will  then  rise  like  a  balloon. 

The  curious  effect  of  hydrogen  upon  sound  may  be  illustrated  by 
placing  in  a  large  bell-glass,  suspended  mouth  downward  and  filled 
with  this  gas,  one  of  the  squeaking  images  used  as  toys  for  children. 
As  the  image  passes  up  into  the  gas,  the  sound  is  observed  to  be 
greatly  enfeebled  and  altered  considerably  in  character.  The  same 
fact  may  be  shown  with  the  human  voice  by  filling  the  lungs  with 
the  gas,  and  then  speaking.  Especial  care  should  be  taken,  however, 
to  have  the  gas  for  this  purpose  made  from  pure  materials ;  for, 
although  the  lungs  may  be  filled  once  with  hydrogen  gas  without 
injury  if  it  is  pure,  yet  it  is  liable  to  contain  impurities  which  may 
produce  serious  results. 

II.  CHEMICAL.  —  Hydrogen  gas  is  combustible  ;  that  is, 
when  heated  to  a  certain  degree — about  500° — it  is  capable 
of  combining  with  the  oxygen  of  the  air  with  the  evolution 
of  light  and  heat.  The  flame  of  burning  hydrogen  is  pale, 
and,  under  the  atmospheric  pressure,  is  scarcely  luminous; 
though  it  becomes  bright  if  the  pressure  be  increased.  The 
heat  evolved  by  it  is  very  great ;  one  gram  of  hydrogen  in 
burning  produces  heat  sufficient  to  raise  34,180  (Thomsen) 
grams  of  water  from  0°  to  1°;  that  is,  34,180  heat-units.  It 
does  not  support  combustion  or  respiration ;  a  lighted  candle 
placed  in  it  is  extinguished  and  an  animal 
loses  his  life  when  confined  in  it.  It  is 
the  standard  of  atomic  mass  and  of  val- 
ence. 

EXPERIMENTS. — A  cylinder  full  of  the  gas — 
collected  as  shown  in  Fig.  2,  for  example — may 
be  inverted,  and  a  lighted  taper  applied  to  its 
mouth.  The  hydrogen  takes  fire  with  a  slight 
explosion  and  burns  with  its  characteristic  flame. 
If  the  jar  be  held  mouth  downward,  and  the 
candle  be  passed  up  into  it,  as  shown  in  Fig.  4,  Fig.  4.  Combustibility 
the  gas  takes  fire  and  burns  quietly  at  the  open 

end,  while  the  flame  of  the  candle,  as  it  passes  into  the  gas,  is  extin- 
guished, but  may  be  relighted  again  from  the  burning  hydrogen  as  it 
is  withdrawn. 


104 


L\0/{<;  A  XI  ('  CHEMISTRY. 


The  combustibility,  and  at  the  same  time  the  levity,  of  hydro- 
gen may  be  shown  by  covering  a  bell-glass  of  this  gas  with  a  glass 
plate,  and  holding  it,  mouth  upward,  beneath  a  lighted  candle  six  or 
eight  inches  distant.  On  removing  the  plate  the  gas  rises  from  the 
bell,  comes  in  contact  with  the  flame  and  takes  fire 
with  a  slight  explosion.  The  same  fact  is  shown 
by  pouring  a  bell-glass  full  of  this  gas  upward  into 
an  empty  bell,  testing  each,  after  the  experiment, 
with  a  lighted  candle.  If  the  soap-bubbles  above 
mentioned  be  touched  with  a  lighted  taper  as  they 
ascend  (Fig.  5),  they  take  fire  and  burn  with  a  slightly 
yellow  flame. 

Water  is  the  sole  product  of  the  combus- 
tion of  hydrogen.      Hence  its  name,  from 
and    evvctw   water-former. 


Fig.  5.  Lighting  a 


"When  burned  from  a  jet,  as  shown  in  Fig.  6  — 

being  previously  dried  by  passing  it  through  a  tube 

containing  calcium  chloride  —  the  flame  of  hydro- 

gen, though  pale,  is  very  hot,  and  will  raise  a  small 

coil  of  fine  platinum  wire  placed  within  it  to  a  white 

heat.     On  holding  a  cold  and  dry  bell-glass  over 

this  flame,  it  is  at  once  dimmed 
with  the  moisture,  and  if  the  ex- 
periment be  sufficiently  long-con- 
tinued the  water  produced  will 
run  down  the  sides  of  the  bell- 
glass  in  drops. 


Several  years  ago  Graham 
pointed  out  the  fact  that  hy- 
drogen is  capable  of  being 
absorbed  or  occluded  by  many 
metals,  at  temperatures  more 
or  less  elevated.  Of  these 
Fig.  6.  Water  from  the  combustion  of  metals,  palladium  is  the  most 

remarkable,   being   able   to 

take  up  over  nine  hundred  times  its  volume  of  hydrogen  at 
ordinary  temperatures,  forming  a  white  metallic  solid,  con- 


USES  OF  HYDROGEN.  105 

taining  its  constituents  in  ratios  nearly  atomic.  Graham 
maintained  that  the  hydrogen  in  this  substance  is  a  solid 
metal,  with  a  density  about  2,  and  analogous  in  many  respects 
to  magnesium  ;  that  it  has  a  metallic  luster,  a  certain  amount 
of  tenacity,  conducts  heat  and  electricity  readily,  and  is  mag- 
netic. He  therefore  proposed  for  it  the  name  hydrogenium. 

14O.  Uses. — On  account  of  its  lightness,  it  has  been  used 
to  fill  balloons  for  military  and  other  purposes.  The  amount 
which  a  balloon  will  carry  up,  i.  e.,  its  ascensional  power,  is 
the  difference  between  the  weight  of  the  balloon  itself  with 
its  contained  hydrogen,  and  that  of  an  equal  volume  of  air. 
A  liter  of  hydrogen  gas  has  an  ascensional  force  of  1*2 
grams. 

Hydrogen  is  used  also  in  the  arts  as  a  heating  material, 
on  account  of  the  high  temperature  developed  by  its  com- 
bustion. 


106  INORGANIC  CHEMISTRY. 


EXERCISES. 

1.  Mention  some  substances  which  contain  hydrogen. 

2.  Write  the  equation  which  expresses  the  preparation  of  hydro- 
gen by  the  action  of  potassium  upon  water. 

3.  Give  the  reaction  which  takes  place  when  iron  acts  on  sulphuric 
acid. 

4.  Ten  grams  of  water  will  give  how  many  grams  of  hydrogen 
when  decomposed  by  heat?     By  the  action  of  sodium? 

5.  How  many  cubic  centimeters  in  each  case  ? 

6.  How  many  grams  of  sodium  will  be  required  ? 

7.  Ten  liters  of  hydrogen  are  desired;  how  many  grams  of  zinc 
are  necessary  to  furnish  this  quantity?    How  many  grams  of  iron? 

8.  Twenty  grams  magnesium  will  yield  how  many  liters  of  hydro- 
gen?    How  many  grams  of  potassium  hydrate  must  be  employed? 

9.  "What  will  hydrogen   cost  per  cubic  meter,  when-  made  with 
iron  costing  7  cents  and  sulphuric  acid  costing  15  cents  per  kilogram? 
When  made  with  zinc  costing  22  cents  per  kilogram  ? 

10.  What  volume  of  hydrogen  does  one  liter  of  vrater  contain? 
One  liter  of  water-vapor  or  steam? 

11.  What  volume  does  0-423  gram  of  hydrogen  occupy  at  0°?    At 
15°?     At  100°? 

12.  Calculate  the   specific  gravity  of  hydrogen  from  its  relative 
density. 

13.  To  what  temperature  must  air  be  raised  to  have  the  relative 
density  of  hydrogen  at  0°? 

14.  Under  what  barometric  pressure  has  air  the  relative  density  of 
hydrogen? 

15.  From  what  does  the  name  hydrogen  come  ? 

16.  What  is  a  unit  of  heat?     How  many  heat-units  does  hydrogen 
produce  in  its  combustion  ? 

17.  How  many  grams  of  hydrogen  must  be  burned  to  raise  50  kilo- 
grams of  water  from  0°  to  10°? 

18.  What  must  be  the  diameter  of  a  spherical  balloon  which,  when 
filled  with  hydrogen,  will  have  an  ascensional  force  of  80  kilograms; 
the  balloon  itself  weighing  30  kilograms? 

19.  What  will  it  cost  to  inflate  the  above  balloon,  if  the  hydrogen 
be  prepared  by  the  use  of  sodium  at  two  dollars  the  kilogram? 


PREPARATION  OF  CHLORINE.  107 


CHAPTER   SECOND. 

NEGATIVE  MONADS. 

§  1.    CHLORINE. 

Symbol  Cl.  Atomic  mass  35-37.  Valence,  I,  III,  V,  and  VII. 
Relative  density  35'37.  Molecular  mass  70'74.  Molecular 
volume  2.  27ie  wows  o/  1  Zifer  a£  0°  is  3-167  grams  (35 -37 
criths). 

147.  History. — Chlorine  was  first  obtained  by  Scheele 
in  1774,  and  called  dephlogisticated  muriatic  acid ;  a  name 
afterward  changed  to  oxymuriatic  acid  by  Berthollet.     In 
1809  G-ay-Lussac  and  Thenard  suggested  its  elementary 
character,  which  was  established  by  Davy  in  1810,  who  gave 
it  the  name  it  bears. 

148.  Occurrence. — Chlorine  never  occurs  free  in  nature. 
In  combination  with  sodium,  magnesium,  potassium  and  cal- 
cium, it  exists  abundantly  in  saline  springs,  and  also  in  sea- 
water,  every  liter  of  which  contains  5  liters   of  chlorine. 
Sodium  chloride  or  salt  exists  also  in  the  solid  form  in  the 
earth,  forming  vast  deposits,  many  of  which,  like  that  at 
Stassfurt,  are  mined. 

149.  Preparation. — Chlorine  may  be  prepared  : 

I.  By  the  action  of  heat  or  of  electricity  upon  chlorides. 

PtCl4       =       PtCl2       +        C12 

Platinic  chloride.     Platinous  chloride.  Chlorine. 

II.  By  the  superior  chemism  of  oxygen  ;  as  when  hydro- 
gen chloride  acts  upon  manganese  di-oxide  : 

(HC1)4   +    Mn02   =    MnCl2    +    (H2O)2    +     C12 

Hydrogen          Manganese         Manganom  Water.  Chlorinf. 

chloride.  di-6xide.  chloride. 


108 


TXOIifi A  XIC  CHKMrSTR T. 


Or,  when  sodium  chloride,  sulphuric  acid  and  manganese 
di-oxide  are  heated  together : 


(Nad),     +     (H.CSO,)), 

Sodium  chloride.           Sulphuric  acid. 

Mn(S04)     4-     Na.2(SO4)     + 

Manganous  sulphate.       Sodium  sulphate. 

+      MuO2     = 

Manganese  di-oxide. 

(H2O)2    4     C 

Water.              Chlo 

EXPERIMENTS. — The  apparatus  employed  for  preparing  chlorine 
is  shown  in  Fig.  7.  The  materials  are  placed  in  a  flask,  which  stands 
in  sand  contained  in  a  thin  iron  cup,  upon  the  gas  furnace.  Through 
the  cork  of  this  flask  two  tubes  pass,  one  for  the  delivery  of  the  gas, 
the  other  a  safety-tube.  This  safety-tube  is  a  funnel-tube  bent  twice 
upon  itself,  upon  the  recurved  portion  of  which  are  two  bulbs.  When 
any  liquid  is  poured  into  the  funnel,  a  portion  remains  in  the  bend 

and  acts  as  a  valve  to 
prevent  the  escape  of 
the  gas.  Should  the 
pressure  within  be  in- 
creased, the  gas  will 
force  the  liquid  up  into 
the  funnel  and  escape 
through  it  in  bubbles; 
should  it  be  diminished, 
the  outside  pressure 
will  force  the  liquid 
into  the  bulbs  and  air 
will  enter,  thus  avoid- 
ing accident.  To  the 
delivery-tube  is  attach- 
ed, by  means  of  a  rub- 
ber tube,  a  bottle  con- 
taining sulphuric  acid, 
to  the  bottom  of  which 
this  delivery-tube  passes,  and  through  which  the  gas  is  made  to  bubble, 
in  order  to  dry  it.  From  this  drying-bottle  it  passes  through  a  long 
glass  tube  to  the  bottom  of  the  cylindrical  gas-jar,  where,  being  heavier 
than  air,  the  gas  gradually  collects.  When  full,  a  fact  easily  ascer- 
tained from  the  green  color  of  the  gas,  the  mouth  of  the  cylinder  is 
closed  with  a  glass  plate  smeared  with  a  little  tallow.  If  a  series  of 
these  jars  be  closed  with  glass  covers  perforated  for  two  tubes,  they 


Fig.  7.  Preparation  of  Chlorine. 


PROPERTIES  OF  CHLORINE.  109 

may  be  successively  filled  by  displacement  with  the  gas.  For  every 
liter  of  chlorine  gas,  8  grams  of  manganese  di-oxide  and  20  grams 
hydrochloric  acid  (of  commercial  strength,  sp.  gr.  about  1-16)  are  re- 
quired. The  acid  is  placed  in  the  flask  first,  the  di-oxide  is  then  added, 
and  the  whole  agitated.  The  evolution  goes  on  for  a  time  without 
heat,  but  to  complete  the  operation  the  gas  beneath  must  be  lighted. 

Commercially,  as  in  Deacon's  process,  the  oxygen  of  the  air  may 
be  used  to  decompose  hydrogen  chloride.  This  process  consists  in 
passing  a  mixture  of  hydrogen  chloride  and  air  through  heated  tubes 
containing  balls  of  clay  soaked  in  a  solution  of  copper  sulphate  and 
dried.  The  copper  sulphate  remains  unchanged,  a  series  of  interme- 
diate compositions  and  decompositions  taking  place.  The  process  is 
continuous,  water  and  chlorine  being  the  only  products.  Weldon's 
process  regenerates  the  MnCl2  by  converting  it  into  CaMnO3,  calcium 
manganite.  And  this,  by  the  action  of  hydrogen  chloride,  produces 
as  before  MnCl2  and  chlorine. 

15O.  Properties. — I.  PHYSICAL. — Chlorine  is  a  yellow- 
ish-green gas — its  name  coming  from  %Aatp6qt  yellowish-green 
— of  a  peculiar  suffocating  odor  and  astringent  taste.  It  is 
totally  irrespirable,  producing  coughing,  even  when  very  di- 
lute, and  in  larger  quantity,  inflammation  of  the  air -pas- 
sages. Its  specific  gravity  is  2*46;  it  is  therefore  nearly  two 
and  one  half  times  heavier  than  air.  Under  a  pressure  of 
four  atmospheres  at  the  ordinary  temperature,  or  when  sub- 
jected without  pressure  to  a  cold  of  —40°,  it  is  condensed 
to  a  dark  yellow  liquid  of  specific  gravity  1-38,  which  boils 
at  — 35*5°  and  solidifies  when  cooled  to  — 102°.  It  is  quite 
soluble  in  water,  one  volume  of  which  at  11°  dissolves  nearly 
three  volumes  of  chlorine  gas,  forming  a  solution  which  pos- 
sesses essentially  the  properties  of  the  gas  itself.  Cooled  to 
0°,  a  definite  molecular  compound  crystallizes  out,  which  con- 
tains, to  every  molecule  of  chlorine,  10  molecules  of  water. 

II.  CHEMICAL. — Chlorine  has  an  exceedingly  strong  at- 
traction for  other  substances.  It  combines  directly  with  all 
the  elements  except  oxygen,  nitrogen,  and  carbon.  When 
finely  divided  copper,  antimony,  or  arsenic  is  placed  in  the 
gas  it  combines  with  it,  with  the  evolution  of  light  and 


110  /.Vo/,v;j.V/Y    CHEMISTRY. 

heat,  to  form  a  chloride.  Phosphorus  at  ordinary  tempera- 
tures, and  sodium  at  more  elevated  ones,  burn  in  chlorine 
spontaneously,  forming  phosphoric  and  sodium  chlorides.  Its 
attraction  for  hydrogen  is  specially  strong,  the  two  gases  ex- 
ploding violently  when  mixed  together  and  exposed  to  sun- 
light, or  on  the  approach  of  a  flame.  In  an  atmosphere 
of  hydrogen,  chlorine  gas  burns  freely,  as  hydrogen  burns 
freely  in  one  of  chlorine.  The  heat  of  the  combustion  of 
hydrogen  in  chlorine  is  less  than  in  oxygen,  being  but  22,000 
(Thomsen)  units.  Chlorine  does  not  burn  in  the  air  at  any 
temperature,  owing  to  its  slight  attraction  for  oxygen. 

ALLOTROPISM.  —  Chlorine  is  capable  of  existing  in  two 
states  or  conditions,  the  one  active,  the  other  passive.  The 
passive  condition  is  the  one  obtained  when  the  chlorine  is 
prepared  in  the  dark ;  when  prepared  in  full  daylight  it 
becomes  exceedingly  active,  capable  of  effecting  unions  not 
before  directly  possible.  Chlorine  prepared  in  the  dark  may 
be  mixed  with  hydrogen,  without  combination  taking  place. 
But  place  the  mixture  in  the  full  sunlight  and  it  at  once 
explodes.  So  a  solution  of  chlorine  in  water,  placed  in  the 
sunlight  in  an  inverted  jar,  loses  its  color,  hydrogen  chloride 
being  formed  and  oxygen  set  free. 

The  existence  of  an  element  in  two  conditions,  in  one  of 
which  it  has  different  properties  from  those  exhibited  by  the 
other,  is  called  allotropism.  The  substance  is  said  to  exist 
in  two  allotropic  states.  It  is  probable  that  allotropism  is 
due  only  to  differences  in  molecular  atomicity. 

One  of  the  most  noticeable  properties  of  chlorine  is  its 
bleaching  power,  due  to  its  attraction  for  hydrogen.  But 
chlorine  will  not  bleach  except  in  the  presence  of  water. 
Water  is  decomposed  by  active  chlorine,  and  the  oxygen 
which  is  thereby  set  free,  being  evolved  in  the  nascent  or 
atomic  state,  destroys  the  vegetable  coloring  matter.  Min- 
eral colors  in  general  are  unaffected  by  chlorine.  In  some 
cases,  however,  the  chlorine  may  combine  with  one  or  more 


PROPERTIES  OF  CHLORINE. 


Ill 


of  the  constituents  of  the  coloring  matter,  forming  thereby 
colorless  compounds.  Its  tendency  to  unite  with  hydrogen 
and  thus  to  destroy  foul-smelling  gases,  of  which  this  hydro- 
gen is  a  constituent,  is  the  cause  of  its  value  as  a  disinfecting 
agent. 

EXPERIMENTS. — The  action  of  chlorine  upon  the  metals  may  be 
shown  by  dropping  into  a  jar  of  the  gas  thin  leaves  of  copper  or 
bronze-leaf,  or  shaking  into  it  some  powdered  arsenic  or  antimony. 
The  metals  burn  spontaneously  and  vividly  as  they  enter  the  gas. 
Phosphorus,  introduced  in  a  combustion- 
spoon— a  cup  attached  to  the  end  of  a  bent 
wire  —  is  instantly 'inflamed.  Sodium,  if 
previously  heated  to  redness,  burns  brill- 
iantly in  a  jar  of  chlorine. 

A  lighted  candle  lowered  into  the  gas 
burns  with  a  smoky  flame  at  first,  as  shown 
in  Fig.  8,  but  is  soon  extinguished.     The  Combustion 
chlorine  takes  the  hydrogen  of  which  the        P°on- 
wax  is  composed,  and  the  carbon  is  set  free  in  the 
form  of  smoke.     A  more  striking  way  of  showing  the 
relative  attractions  of  chlorine  for  hydrogen  arid  for 
carbon  is  shown  in  Fig.  9.     A  jar  of  pure  chlorine  has 
thrust  into  it  a  piece  of  thin  tissue  paper,  previously 
moistened  with  warm  oil  of  turpentine.    The  chlorine 
seizes  the  hydrogen  of  the  turpentine,  evolving  so 
much  heat  in  the  combination  that  the  whole  takes 
fire,  evolving  dense  clouds  of  smoke. 

Either  the  gas,  or  its  solution  in  water,  may  be 
used  to  show  its  bleaching  power.  Pieces  of  print 
having  various  designs  upon  them  in  color,  when 
moistened  and  placed  in  contact  with  the  chlorine, 
will  have  their  colors  discharged.  A  piece  of  paper 
covered  with  characters,  partly  written  and  partly 
printed,  loses  entirely  all  the  writing  upon  it  when 
placed  in  chlorine;  the  writing-ink  being  attacked, 
while  the  printing-ink,  made  of  carbon,  is  unaffected.  Fig. 9.  Turpentine 

The  action  of  oxygen  upon  hydrogen  chloride  to        in  chlorine- 
set  free  chlorine  and  the  apparently  contradictory  action  of  chlorine 
upon  hydrogen  oxide  to  set  free  oxygen  afford  an  interesting  example 


Fig.  8.   Candle 

burning  in 

Chlorine. 


112  jxona.ixrc  CHEMISTRY. 


of  the  law  of  maximum  work.  Since  to  form  a  molecule  of  water- 
vapor  57,160  heat-units  are  evolved,  while  to  decompose  two  mole- 
cules of  gaseous  hydrogen  chloride  only  44,000  heat-units  are  absorbed, 
the  reaction  C12 


is  evidently  an  exothermic  reaction  and  therefore  takes  place  without 
outside  aid.  So,  on  the  other  hand,  since  the  formation  of  two  mole- 
cules of  hydrogen  chloride  in  solution  in  water  evolved  78,630  heat- 
units,  while  the  decomposition  of  one  molecule  liquid  water  absorbs 
only  68,360  heat-  units,  the  converse  reaction 

H20  +  C12  =  (HOI),  -f  O 

is  also  exothermic,  and  under  the  given  circumstances  will  take  place 
without  the  assistance  of  external  energy. 

151.  Tests.  —  Free  chlorine  may  be  detected  readily  by 
its  odor,  and,  if  pure,  by  its  color,  its  bleaching  action  upon 
indigo,  and  by  the  dense  white  fumes  which  it  gives  with 
ammonia.     In  solution,  it  is  detected  by  its  power  of  dis- 
solving gold  leaf.     In  combinations,  it  yields  with  solutions 
of  silver  salts  a  white  precipitate  of  silver  chloride,  insoluble 
in  nitric  acid. 

152.  Uses.  —  Chlorine  is  used  very  largely  in  the  arts  for 
the  preparation  of  the  so-called  chloride  of  lime,  the  form  in 
which  this  gas  is  made  available  as  a  bleaching  agent.     The 
process  employed  on  the  large  scale  is  the  second  given  in  a 
former  section.     Salt  and  sulphuric  acid,  together  with  man- 
ganese di-oxide,  or  sometimes  nitric  acid,  are  heated  together 
in  large  leaden  vessels,  and  the  gas  as  produced  is  conducted 
into  long,  low,  stone  chambers,  upon  the  floor  of  which  dry 
slacked  lime  is  placed  for  the  purpose  of  absorbing  it. 

COMPOUNDS   OF    CHLORINE   WITH   HYDROGEN. 

HYDROGEN  CHLORIDE.  —  Formula  HC1.  Molecular  mass  36-37. 
Molecular  volume  2.  Relative  density  18*18.  The  mass  of  1 
liter  at  0°  is  1*63  grams  (18-18  crtihs). 

153.  History.  —  Only  one  compound  of  chlorine  and  hy- 
drogen is  known  ;  this  is  hydrogen  chloride,  or  as  it  is  more 


PREPARATION  OF  HYDROGEN  CHLORIDE. 


113 


frequently  called,  hydrochloric  acid.  It  was  known  to  the 
alchemists  under  the  name  "  spirit  of  salt."  Glauber  in  the 
17th  century  gave  it  the  name  muriatic  acid,  from  the  Latin 
muria,  brine.  The  pure  gas  was  first  obtained  by  Priestley 
in  1772,  though  it  was  not  till  1810  that  its  true  composition 
was  ascertained  by  Davy. 

154.  Preparation. — I.  Since  chlorine  and  hydrogen  are 
both  monads,  and  their  molecules  are  both  di-atomic,  it  fol- 
lows that  they  unite  in  equal  volumes.  Hydrochloric  acid 
may  be  formed  therefore  by  the  direct  union  of  equal  volumes 
of  its  constituents,  according  to  the  equation : 

H2  +  C12  =  (HC1)2 

This  equation  also  declares  that  the  volume  of  the  hydrogen 
chloride  is  the  same  as  that  occupied  by  the  hydrogen  and 
chlorine  which  formed  it.  \ 

EXPERIMENTS. — If  a  suitable 
jar  be  filled,  one  half  with  hydro- 
gen, the  other  half  with  chlorine, 
and  a  flame  be  applied  to  the 
open  mouth  as  shown  in  Fig.  10, 
a  smart  explosion  takes  place, 
and  white  fumes  of  hydrochloric 
acid  are  formed.  In  this  experi- 
ment it  is  well  to  wrap  a  towel 
about  the  cylinder,  to  prevent 
the  pieces  from  flying  in  case  of 
breakage.  If  the  glass  be  strong 
enough,  the  mixture  of  gases  may 
be  exploded  by  exposing  the  jar 
to  sunlight.  On  opening  it  after- 
ward, with  the  mouth  under  mer- 
cury, none  will  enter,  thus  show- 
ing that  the  volume  of  the  hydrochloric  acid  produced  is  the  same  as 
that  of  the  chlorine  and  hydrogen  before  union. 

II.  The  second  method  of  preparing  hydrochloric  acid, 
and  the  one  usually  employed,  is  by  the  action  of  sulphuric 


Fig.  10.  Direct  union  of  Hydrogen  and 
Chlorine. 


114 


INORGANIC  CHEMISTS  Y. 


acid  upon  a  chloride,  generally  sodium  chloride,  or  salt.    The 
reaction  is : 

(Nad),     +     H2(S04)    =     Na2(S04)    +      (HC1)2 

Sodium  chloride.      Hydrogen  sulphate.      Sodium  sulphate.      Hydrogen  chloride. 

By  passing  the  gas  thus  set  free  through  water  so  long  as  it 
is  absorbed,  the  liquid  acid  is  obtained. 

EXPERIMENTS. — For  the  preparation  of  the  gas  from  salt  and  sul- 
phuric acid,  the  apparatus  shown  in  Fig.  11  may  be  employed.  The 
salt  is  placed  in  the  flask,  and  upon  it  is  poured,  through  the  safety- 
tube,  twice  its  weight  of  sulphuric  acid,  previously  diluted  with  one- 


Fig.  11.  Preparation  of  Hydrochloric  Acid. 

fourth  its  volume  of  water.  Upon  applying  a  gentle  heat,  the  gas 
is  copiously  evolved,  and  may  be  collected  either  over  mercury  or  by 
displacement. 

If  it  is  desired  to  obtain  the  liquid  acid,  the  gas  is  passed  through 
water  contained  in  the  series  of  bottles  shown  in  the  figure,  called 
Woulfe's  bottles.  The  first  bottle,  which  is  smaller  than  the  others, 
contains  water  to  wash  the  gas,  which  then  passes  into  the  larger 
bottles,  charging  the  water  in  each  in  succession. 

155.  Properties. — Hydrogen  chloride  is  a  colorless,  pun- 
gent, acid  gas,  which  fumes  strongly  in  the  air,  is  irrespira- 
ble,  and  extinguishes  flame.  Its  critical  temperature  is  52*3°, 
and  its  critical  pressure  is  86  atmospheres ;  so  that  when  sub- 


PROPERTIES  OF  HYDROGEN  CHLORIDE. 


11") 


jected  to  a  pressure  of  40  atmospheres  at  10°,  or  of  2  atmos- 
pheres at  — 70°,  it  is  condensed  to  a  colorless  limpid  liquid 
having  a  specific  gravity  of  1'27,  boiling  at  —  8O3°  under 
atmospheric  pressure,  and  solidifying  at  —116°.  It  is  re- 
markably soluble  in  water,  one  volume  of  which  dissolves 
450  volumes  of  this  gas  at  15°,  forming  the  liquid  acid. 
This  acid  contains  about  43  per  cent  of  hydrogen  chloride, 
and  has  a  specific  gravity  of  1*21;  when  heated  it  evolves 
hydrochloric  acid  gas,  until,  under  the  ordinary  atmospheric 
pressure,  the  solution  has  a  specific  gravity  of  1*104,  and 
contains  20 '22  per  cent  of  the  gas ;  then  the  boiling  point 
remains  stationary  at  110°,  and  the  liquid  distills  over  un- 
changed. 


Fig.  12.  Commercial  Preparation  of  HC1. 

The  composition  of  hydrogen  chloride  may  be  determined 
by  analysis.  If  two  volumes  of  the  gas  be  acted  on  by  potas- 
sium, only  one  volume  remains  and  that  is  hydrogen.  In  a 
similar  way  the  electrolysis  of  a  solution  of  hydrogen  chloride 


116  ixoita.iMc  r ///•;. 

*> 

yields  equal  volumes  of  chlorine  and  of  hydrogen.  Hence, 
since  this  substance  contains  equal  volumes  of  hydrogen  and 
chlorine,  there  must  be  35*37  units  of  mass  of  chlorine  for 
every  unit  of  mass  of  hydrogen. 

EXPERIMENTS. — The  solubility  of  hydrogen  chloride  in  water,  and 
at  the  same  time  its  acidity,  may  be  shown  by  removing  .the  stopper 
of  a  tall  cylinder  filled  with  the  dry  gas,  beneath  the  surface  of  water 
colored  with  blue  litmus  solution.  On  agitating  the  vessel  a  little,  the 
water  enters  as  if  into  a  vacuum,  the  cylinder  being  not  (infrequently 
broken. 

On  cooling  the  concentrated  solution  to  — 22°,  a  compound  with 
water  separates  in  the  form  of  crystals  having  the  formula  HC1(H2O)2. 

156.  Uses. — Hydrochloric  acid  is   manufactured  on  an 
immense  scale  in  the  arts,  chiefly  as  a  waste  product  in  the 
soda  industry.     The  salt  is  treated  with  sulphuric  acid  in 
cast  iron  cylinders  placed  in  a  furnace,  as  shown  in  Fig.  12, 
and  the  gas  as  evolved  is  condensed  in  water  contained  in 
large  Woulfe  bottles  made  of  earthenware.     It  is  used  for 
various  minor  purposes  in  the  chemical  arts. 

§  2.    BROMINE,  IOL>INE,  AND  FLUORINE. 

BROMINE. — Symbol  Br.  Atomic  mass  79*76.  Valence  I,  V, 
and  VII.  Specific  gravity  3*187  at  0°.  Relative  demity  of 
vapor  79*76.  Molecular  weight  159*5.  Molecular  volume  2. 
The  mass  of  1  liter  of  bromine-vapor  at  0°  is  7*15  grams 
(79*76  criihs). 

157.  History.  —  Bromine  was  discovered  in  the  water 
of  the  Mediterranean  sea  by  Balard,  in  1826.     On  account 
of  its  disagreeable  odor,  he  gave  it  the  name  bromine,  from 
Ppwtjun;,  stench. 

158.  Preparation. — On  evaporating  the  water  of  many 
saline  springs,  the  salt  crystallizes  out,  and  there  is  left  a 
solution  of  the  more  soluble  salts  —  called  the  mother-liquor 
or  bittern — which  is  rich  in  bromides.     By  heating  this  bit- 


PROPERTIES  OF  BROMINE  AND  IODINE.  117 

tern  with  manganese  di-oxide  and  sulphuric  acid,  the  chlo- 
rides in  it  are  decomposed,  yielding  chlorine,  which,  in  its 
turn,  sets  the  bromine  free  from  the  bromides.  The  vapors 
of  the  bromine  are  led  into  a  cooled  receiver,  where  they 
condense  into  a  liquid. 

159.  Properties. — Bromine  is  a  heavy,  dark  brownish- 
red  liquid,  of  a  disagreeable  odor,   somewhat  recalling  that 
of  chlorine.     At  a  temperature  of  63°  it  boils,  and  is  con- 
verted into  a  deep  red  vapor  which  is  five  and  one  half  times 
denser  than  air.     Cooled  to  —22°,  it  becomes  a  dark,  lead- 
gray  crystalline  solid,  with  a  metallic  luster.    It  is  but  slightly 
soluble  in  water,  thirty-three  parts  of  which  dissolve,  at  15°, 
but  one  part  of  bromine. 

Chemically  it  is  similar  to  chlorine,  but  less  active.  Hence 
chlorine  sets  it  free  from  its  combination.  Several  of  the 
metals  burn  in  its  vapor,  and  it  exerts  a  decided  bleaching 
action.  It  is  an  active  corrosive  poison. 

Bromine  colors  starch  yellow ;  and  a  bromide  in  aqueous 
solution  precipitates  silver  from  its  solutions,  as  yellow  silver 
bromide.  It  is  used  principally  in  photography  and  in  med- 
icine. 

IODINE. — Symbol  I.  Atomic  mass  126 '54.  Valence  I,  III,  V, 
and  VII.  Specific  gravity  4'95.  Relative  vapor-demity  126 '54. 
Molecular  mass  253*08.  Molecular  volume  2.  The  mass  of 
1  liter  of  iodine-vapor  at  0°  is  11*37  grams  (126'54  criths). 

160.  History. — On  the  coasts  of  Scotland  and  Normandy 
large  masses  of  sea-weeds  were  formerly  burned  in  order  to 
extract  the  soda  which  they  contain.     The  semi-fused  ash — 
called  kelp  or  varec — was  dissolved  in  water  and  the  soda 
salts  crystallized  out.     It  was  in  the  mother-liquor  thus  ob- 
tained that  iodine  was  first  discovered  by  Courtois  in  1811. 
Its  elementary  character  was  determined  by  Davy  and  G-ay- 
Lussac  in  1813.     Its  name  is  from  Mys,  violet-colored,  in 
allusion  to  the  beautiful  color  of  its  vapor. 


118  I \OUGAXIC  CHEMISTRY. 

1O1.  Preparation. — It  is  prepared  commercially  in  the 
same  way  as  bromine,  by  distilling  the  mother-liquors  just 
mentioned  with  manganese  di-oxide  and  sulphuric  acid,  and 
condensing  the  vapors ;  or  by  passing  chlorine  or  nitrous 
acid  through  the  mother-liquors,  when  the  iodine  will  fall  as 
a  precipitate. 

1G2.  Properties. — Iodine  is  a  bluish-black  solid,  having 
a  metallic  luster,  and  crystallizing  in  rhombic  scales,  or,  not 
infrequently,  in  well-defined  ortho-rhombic  octahedrons,  Fig. 
13.  Heated  to  107°  it  melts,  and  at  180°  boils,  evolving  a 
dense,  magnificent  violet  vapor,  which 
is  8 '72  times  heavier  than  air,  and  is 
therefore  the  heaviest  vapor  known. 
At  1500°,  however,  the  relative  density 
of  the  vapor  is  reduced  one  half;  and 
hence  the  molecule  is  monatomic.  It 
Fig.  is.  crystals  of  iodine.  **  onl>;  Rightly  soluble  in  water,  one 
part  of  iodine  requiring  7,000  parts  of 

water  at  ordinary  temperatures  to  dissolve  it.  It  dissolves 
readily  in  alcohol,  ether,  carbon  disulphide  and  chloroform ; 
and  also  in  aqueous  solutions  of  potassium  iodide. 

In  chemical  activity  it  is  third  in  the  series,  being  next  to 
bromine.  It  bleaches  but  faintly,  if  at  all,  in  full  sunlight, 
but  combines  directly  with  the  metals,  forming  iodides.  It 
stains  the  skin  yellow,  but  is  not  an  active  poison. 

Starch  is  a  characteristic  reagent  for  free  iodine.  It  strikes 
with  it  a  deep  blue  color,  which  is  so  intense  that  one  part 
of  iodine  may  be  detected  by  it  in  300,000  parts  of  water. 
The  most  delicate  test  for  iodine  is  the  purple-red  color  it 
produces  when  dissolved  in  carbon  disnlphide.  One  part  of 
iodine  in  1,000,000  parts  of  water  may  be  detected  in  this 
way.  Soluble  iodides  produce  characteristic  precipitates  with 
mercurous,  mercuric,  and  lead  salts. 

EXPERIMENTS. — The  process  of  obtaining  iodine  maybe  illustrated 
by  adding  to  a  solution  of  potassium  iodide  contained  in  a  test-tube  n 


I'UEPAKATION  AND  PJiOrKRTIES  OF  FLUORINE.     119 

few  drops  of  chlorine-water.  The  liquid  becomes  brown  in  color  from 
the  iodine  set  free,  and  upon  agitating  it  with  ether,  the  iodine  is  dis- 
solved by  the  ether  and  forms  a  dark  brown  layer  above,  while  the 
solution  below  is  colorless.  Upon  pouring  off  the  ether  and  agitating 
it  with  a  little  solution  of  potassium  hydrate,  potassium  iodide  is 
formed  and  the  ether  is  decolorized. 

The  fumes  of  iodine  are  conveniently  exhibited  by  throwing  some 
iodine  upon  a  heated  brick,  and  then  covering  the  whole  with  a  large 
bell-glass.  To  show  its  reaction  with  starch,  add  a  drop  of  the  alco- 
holic solution  to  a  very  dilute  solution  of  starch  contained  in  a  tall 
jar.  The  blue  color,  upon  agitation,  will  penetrate  the  entire  mass.*" 
This  experiment  may  be  modified  by  adding  a  few  drops  of  potassium 
iodide  to  a  dilute  solution  of  starch,  and  then  a  few  drops  of  chlorine- 
water.  The  iodine  does  not  color  the  starch  until  set  free  by  the 
chlorine,  when  the  blue  appears. 

Add  a  few  drops  of  potassium  iodide  to  some  water  contained  in 
each  of  three  tall  test-glasses.  Upon  dropping  into  the  first  a  little 
of  a  solution  of  lead  acetate,  a  brilliant  yellow  precipitate  of  lead 
iodide  is  obtained.  The  second,  treated  with  a  few  drops  of  mercu- 
rous  nitrate,  gives  a  bright  yellowish-green  precipitate  of  mercurous 
iodide.  While  the  third,  upon  the  addition  of  a  little  mercuric  chlo- 
ride, gives  scarlet  mercuric  iodide. 

163.  Uses. — Iodine  is  largely  used  in  medicine,  both  free 
and  in  combination.     It  is  particularly  serviceable  in  gland- 
ular affections.     It  is  also  used  extensively  in  photography 
and  in  the  preparation  of  aniline  colors. 

FLUORINE. — Symbol  F.  Atomic  mass  19 '06.  Valence  III  (?). 
Molecular  mass  38*12  (?).  Molecular  volume  2  (?).  Relative 
density  19'06  (?).  The  mass  of  1  liter  at  0°  is  1-7  grams 
(19-06  criths)  (?). 

164.  Preparation  and  Properties. — The  mineral  known 
as  fluorite,  fluor  or  Derbyshire  spar,  is  a  compound  of  fluor- 
ine with  calcium,  CaF2;  and  the  mineral  cryolite  is  sodio- 
alumiimm  fluoride,  Na.{AlF(i.     From  either  of  these  minerals 
hydrogen  -  potassium  fluoride  may  be  prepared,  and  by  the 
action  of  heat  on  this,  anhydrous  hydrogen  fluoride  is  ob- 


120  INORGANIC  CHEMISTRY. 

tained.  By  the  electrolysis  of  this  substance  placed  in  a 
V-tube  of  platinum  and  cooled  to  — 23°  by  boiling  meihyl 
chloride,  Moissan  obtained  at  the  positive  electrode  a  color- 
less gas,  having  an  odor  like  that  of  hypochlorous  acid,  and 
possessed  of  an  extraordinary  activity.  It  unites  directly 
with  hydrogen  even  in  the  dark,  and  decomposes  water  read- 
ily, setting  free  ozonized  oxygen.  Sulphur,  selenium,  phos- 
phorus, iodine,  arsenic,  antimony,  silicon,  boron,  potassium, 
and  sodium  take  fire  in  it  spontaneously.  Potassium  chlo- 
ride and  iodide  are  attacked  by  it  when  melted,  the  chlorine 
and  iodine  being  set  free.  Carbon  disulphide  is  inflamed  by 
it ;  and  carbon  tetrachloride  evolves  chlorine  when  this  gas 
is  led  into  it.  Organic  substances  are  violently  attacked  and 
inflamed  in  it.  Quantitative  experiments  with  iron  showed 
the  absence  of  every  other  substance,  and  proved  the  gas 
thus  obtained  to  be  fluorine.  It  therefore  appears  that  the 
activity  of  fluorine  surpasses  that  of  all  the  other  elements. 

By  igniting  platinum  fluoride,  Moissan  has  obtained  fluor- 
ine in  a  purer  form.  Its  name  comes  from  that  of  the  min- 
eral fluor  spar  just  mentioned.  Fluorite  comes  from  the 
Latin  fluo,  I  flow,  because  it  is  used  as  a  flux  in  the  reduc- 
tion of  metals. 

HYDROBROMIC,  HYDRIODIC    AND    HYDROFLUORIC    ACIDS. 

165.  Hydrogen  Bromide  or  Hydrobromic  Acid.— 

Formula  HBr.  Molecular  mass  80'76.  Molecular  volume  2. 
Relative  density  40-38. 

Hydrogen  bromide  may  be  obtained  directly  by  passing  a 
mixture  of  hydrogen  and  bromine  vapor  over  heated  plati- 
num finely  divided,  or  indirectly  by  acting  upon  phosphorus 
with  bromine  in  presence  of  water.  The  phosphorus  and 
the  bromine  first  unite  to  form  phosphoric  bromide  accord- 
ing to  the  following  reaction  : 

P.  +   (Br,),,,  -  (PBr5), 


A\l)  HYI)/!OI<'Lr()t;lC  ACIIW.  121 

which,  as  fast  as  formed,  is  decomposed  into  phosphoric  acid 
and  hydrobromic  acid  by  the  water  present  : 

PBr5  +  (H.20)4  =  H:)P04  +  (HBr)5 

Hydrobromic  acid  is  a  colorless  acid  gas,  fuming  strongly 
in  moist  air,  and  very  soluble  in  water.  Cooled  to  —  73°  it 
becomes  a  liquid,  and  this  at  the  temperature  of  —  120° 
freezes. 

1GO.  Hydrogen  Iodide  or  Hydriodic  Acid.  —  Formula 
HI.  Molecular  mass  127  '54.  Molecular  volume  2.  Relative 
density  63  '77. 

Hydrogen  iodide  may  be  readily  prepared  by  heating  to- 
gether potassium  iodide,  iodine,  and  phosphorus,  in  presence 
of  water.  The  reaction  is  analogous  to  that  above  given  for 
hydrogen  bromide  : 

(KI)4      +      P,     +     (I,)5     +     (H,0)8     = 

Potassium  iodide.    Phosphorus.         Iodine.  Water. 


+        (HK,(P04))2 

Ilydrlodic  acid.        Hydro-di-potassium  phosphate. 

Hydriodic  acid  is  also  a  colorless  gas,  of  specific  gravity 
4-41,  which  has  an  acid  reaction  and  fumes  in  the  air.  It 
is  easily  condensed  to  a  liquid  by  a  pressure  of  four  atmos- 
pheres at  0°,  and  this  liquid,  cooled  to  —51°,  freezes  to  a 
clear  ice-like  solid.  It  is  as  soluble  in  water  as  hydrogen 
chloride,  yielding  at  0°  a  solution  of  specific  gravity  1'99. 
A  weaker  solution,  of  specific  gravity  1/7,  distills  over  at 
127°,  and  contains  57  per  cent  of  hydrogen  iodide.  This 
solution  is  much  used  as  a  reducing  reagent  in  organic  chem- 
istry. At  180°  the  gas  decomposes  into  hydrogen  and  iodine. 

167.  Hydrofluoric  Acid.  —  Formula  HF.  Molecular  mass 
2O06.  Molecular  volume  2.  Relative  density  10. 

Hydrogen  fluoride  is  generally  prepared  by  the  action  of 
sulphuric  acid  upon  calcium  fluoride  ;  calcium  sulphate  and 
hydrogen  fluoride  resulting  : 

CaF2  +  H.2(S04)  =  Ca(S04)   +   (HF), 


122  r\OI{(!.L\I('  CH 

The  process  must  be  conducted  iu  a  vessel  of  lead  or  of  plat- 
inum, as  the  gas  readily  attacks  glass.  It  may  be  obtained 
anhydrous  by  heating  hydrogen-potassium  fluoride. 

Hydrofluoric  acid  is  a  colorless  gas,  which  fumes  in  the 
air  and  reacts  strongly  acid.  The  anhydrous  gas  condenses  to 
a  liquid  at  0°,  which  boils  at  19'5°,  and  solidities  at  — 102'5° 
as  a  transparent  crystalline  mass,  fusing  again  at  —92-30°. 
As  obtained  by  the  above  reaction,  it  is  a  liquid  having  a 
specific  gravity  of  1'06,  owing  to  the  presence  of  moisture. 
The  strong  acid  corrodes  the  skin  powerfully,  giving  rise 
to  painful  ulcers ;  and  the  fumes,  if  inhaled,  produce  serious 
irritation  of  the  lungs. 

At  temperatures  of  100°  and  above,  hydrogen  fluoride 
has  a  molecular  mass  of  20*06,  corresponding  to  the  formula 
HF ;  but  at  about  30°  its  molecular  mass  is  double  this 
value,  or  H2F.r  It  forms  two  classes  of  salts.  I  IMF,  and 
M.2F.2,  in  which  M  represents  any  metal ;  and  hence  H.,F2 
represents  probably  the  size  of  the  molecule  under  ordinary 
conditions.  If  fluorine  be  trivalent,  the  graphic  formula  of 
hydrogen  fluoride  will  be  H— F=F— H,  and  that  of  cryolite 

F=F-Na 

AlfF=F-Na. 

xF=F-Na 

This  substance  when  moist  is  distinguished  from  all  others 
by  its  remarkable  property  of  attacking  glass.     With  the 
silicon  of  the  glass  the  fluorine  combines 
to  form  a  gaseous  silicon  fluoride.     The 
acid  is  used  extensively  in  the   arts  for 
etching  glass,  the  highly  ornamented  door- 
lights  now  so  common  being  prepared  by 
this  agent.     Used  as  a  liquid,  the  etched 
surface  is  left  smooth  ;  but  when  the  gas 
Etching  by  HF.        is  applied,  the  surface  remains  rough. 

EXPERIMENT. — Place  some  finely  pulverized  fluor-spar  or  cryolite 
in  a  dish  of  lead,  or  preferably  of  platinum  (Fig.  14),  and  pour  upon  it 


RELATIONS  OF  THE  HALOUKX  UlfOt'P.  123 

some  strong  sulphuric  acid.  Cover  the  dish  with  a  glass  plate,  upon 
the  lower  side  of  which  is  a  thin  layer  of  wax,  through  which  some 
characters  have  been  drawn  with  a  iiii-e  point.  Place  the  whole  on  a 
suitable  stand  and  heat  very  gently  for  a  few  minutes.  If  now  the 
wax  bo  removed  from  the  plate,  the  device  drawn  will  be  found  etched 
upon  the  glass. 


§  3.    RELATIONS  OF  THE  HALOGEN  GROUP. 

168.  Chlorine,  bromine,  and  iodine  constitute  a  closely 
allied  group  of  elements.  Even  in  their  physical  properties, 
there  is  a  remarkable  progression  observable.  As  to  physical 
state,  chlorine  is  a  gas,  bromine  a  liquid,  iodine  a  solid;  as 
to  color,  chlorine  is  yellowish-green,  bromine-vapor  is  brown, 
iodine-vapor  purple  ;  as  to  density,  chlorine  comes  first,  then 
bromine,  then  iodine.  All  of  them  exist  in  the  solid,  liquid, 
and  gaseous  forms,  and  change  from  one  to  the  other  at  tem- 
peratures not  far  apart. 

The  same  is  true  of  their  chemical  properties.  The  atomic 
mass  of  bromine,  79*76,  is  nearly  a  mean  between  that  of 

126-54+35-37 
chlorine  and  iodine,  -  —  =8U'yD.    Chlorine  is  more 

2 

active  than  bromine,  and  bromine  more  than  iodine.  Indeed, 
as  is  frequently  the  case  with  allied  negative  elements,  the 
chemism  seems  to  vary  inversely  as  the  atomic  weight.  As 
a  whole,  therefore,  the  group  furnishes  an  excellent  illustra- 
tion of  the  periodic  law  (page  23). 

Moreover,  the  hydrogen  compounds  of  these  elements  are 
similarly  constituted  and  exhibit  a  similar  gradation  in  prop- 
erties. Their  binary  compounds  with  potassium  and  sodium 
all  resemble  sea-salt ;  hence  these  compounds  are  frequently 
called  haloid  salts,  and  the  elements  halogens. 


124  IXOUGAMC  CHEMISTRY. 


EXERCISP]S. 


1.  In  what  compounds  does  chlorine  occur  in  nature? 

2.  What  volume  does  32  grains  of  chlorine  occupy? 

3.  What  is  the  mass  of  2356  cubic  centimeters  ? 

4.  How  many  grams  of  platinic  chloride  are  required  to  give  25 
grams  of  chlorine?     To  give  500  cubic  centimeters? 

5.  How  many  liters  of  chlorine  from  20  grams  of  hydrochloric 
acid  gas?     How  much  manganese  di-oxide  is  needed? 

6.  Liquid  hydrochloric  acid  of  specific  gravity  1-20  contains  41  per 
cent  of  HC1  ;  one  liter  will  yield  how  many  liters  of  chlorine? 

7.  Commercial  manganese  di-oxide  is  seldom  pure;  what  per  cent 
of  MnO2  does  a  sample  contain,  30  grams  of  which  heated  with  HC1, 
gives  12-04  grams  chlorine? 

8.  One  kilogram  of  salt  contains  how  many  grams  of  chlorine? 

9.  One  cubic  centimeter  salt  contains  how  many  cubic  centimeters 
of  chlorine?     (Specific  gravity  of  salt  2-15.) 

10.  150  liters  of  chlorine,  at  15°,  and  under  742  mm.  pressure,  are 
required;  how  many  grams  of  salt,  of  sulphuric  acid,  and  of  manga- 
nese di-oxide,  are  necessary? 

11.  Give  the  formulas  and  names   of  the  compounds  of  chlorine 
with  Ag't  Cu",  Co",  Sb'",  B'",  Sn'v,  Ti'v,  PV. 

12.  Calculate  the  percentage  composition  of  silver  chloride. 

13.  If  ten  c.  c.  of  hydrogen  diffuse  into  an  atmosphere  of  chlorine 
in  one  minute,  how  much  chlorine  will  diffuse  into  the  hydrogen  in 
the  same  time? 

14.  One  cubic  meter  of  HC1  contains  what  mass  of  Cl? 

15.  What  volume  of  Cl  will  convert  one  liter  of  H  into  HC1? 

16.  Calculate  the  specific  gravity  of  HC1  from  its  relative  density. 

17.  What  volume  has  one  kilogram  of  HC1  gas? 

18.  One  liter  of  HC1  passed  over  heated  iron,  yields  what  volume 
of  hydrogen? 

19.  Write  the  reaction  which  takes  place  in  replacing  the  sodium 
in  salt  by  hydrogen. 


Kti.  J25 

20.  How  many  kilograms   of  HC1  gas  may  be  obtained  from  28 
kilograms  of  salt?     How  many  liters? 

21.  How  much  sulphuric  acid  would  be  required  to  decompose  it? 
How  much  Na.2(SO4)  would  be  obtained? 

22.  One  liter  of  liquid  acid,  specific  gravity  1-21,  contains  how  many 
grams  of  HCl?     How  many  liters? 

23.  How  many  kilograms  of  salt  and  of  sulphuric  acid  are  required 
to  produce  150  kilograms  of  liquid  HCl,  containing  24-24  per  cent 
of  the  gas  ? 

24.  What  mass  of  potassium  hydrate  is  required  to  neutralize  one 
liter  of  hydrochloric  acid  gas? 

25.  Ten  grams  of  the  liquid  acid  precipitated  2-26  grains   silver 
chloride  from  11  solution  of  silver;   what  percentage  of  HCl  did  the 
solution  contain? 

§2. 

26.  What  is  the  mass  of  one  c.  c.  bromine-vapor  at  150°  and  760 
mm.? 

27.  Fifty  c.  c.  of  HBr  decomposed  by  Na,  gives  what  volume  of  H? 

28.  What  volume  of  HBr  will  10  grams  of  Br  give? 

29.  If  a  liter  of  HI  and  one  of  chlorine  be  mixed  together,  what 
will  be  the  reaction?    What  will  be  the  resulting  gaseous  volume  and 
what  its  composition?  - 

30.  Show  that  the  liquid  hydriodic  acid  which  contains  57  per  cent 
of  HI,  is  not  a  definite  hydrate. 

31.  What  volume  does  100  grams  of  H2F2  occupy? 

32.  What  volume  of  H  is  contained  in  250  c.  c  of  H2F2  ? 


126  IXOliGAMC  CHEMISTRY. 


CHAPTER  THIRD. 

NEGATIVE  DYADS. 
S  1.    OXYGEN. 

Symbol  O.  Atomic  mass  15 '96.  Valence  II.  Relative  demity 
15-98.  Molecular  mass  31 '92.  Molecular  volume  2.  The 
mass  of  1  liter  at  0°  is  1*4298  grams  (15 '96  critli*). 

169.  History. — Oxygen  was  discovered  by  Priestley  in 
1774,  who  called  it  dephlogisticated  air.    The  following  year 
Scheele  discovered  it  independently,  and  gave  it  the  name 
empyreal   air.     Condorcet  called   it  vital   air.     After  the 
overthrow  of  the  theory  of  phlogiston  by  Lavoisier  in  1781, 
he  gave  it  the  name  oxygen,  from  the  Greek  n-^  and  ^>v«w, 
acid-former. 

170.  Occurrence. —  Oxygen  is  the  most  abundant  ele- 
ment in  nature.     It  exists  free  in  the  atmosphere,  of  which 
it  forms  a  fifth  part.     Combined  with  other  elements,  it  con- 
stitutes two  thirds  of  the  entire  globe.    Water  is  eight  ninths 
oxygen,  silica  is  one  half  oxygen,  and  alumina  one  third 
oxygen,  by  weight.     Fully  one  half  of  the  weight  of  all 
minerals,  three  quarters  of  the  weight  of  all  animals,  and 
four  fifths  of  the  weight  of  all  vegetables,  is  oxygen. 

171.  Preparation. — The  atoms  of  compound  molecules 
containing  oxygen  may  be  re-arranged  so  as  to  yield  simple 
oxygen  molecules : 

I.  By  the  action  of  some  physical  agent ;  as 
(a)  Heat. — Mercuric  oxide,  when  exposed  to  a  high  tem- 
perature, is  resolved  into  mercury  and  oxygen : 

Hg  =  O  Hg  O 

becomes  and     l| 

Hg  =  O  Hg  O 


I'll 


(b)  Light.  —  Carbon  di-oxide  in  the  leaves  of  plants  yields, 
under  the  influence  of  sunlight,  carbon  and  oxygen  : 

(CO,),    =     C2     +     (02)2 

(c)  Electricity.  —  In  the  electrolysis  of  oxygen  compounds. 
II.   By  the  chemism  of  some   other   element  assisted  -by 

some  physical  agent,  generally  heat  :  as  when  chlorine  acts 
upon  the  vapor  of  water  at  a  red  heat,  producing  hydrogen 
chloride  and  oxygen  : 

(H.20),    +     (Cl,)2    =    (HC1)4    +    02 
or  upon  calcium  oxide  or  lime,  producing  calcium  chloride 
and  oxygen  : 


(CaO)2    +     (C12)2    =    (CaCl2)2 


O 


EXPERIMENTS.  —  The  original  experiment  by  which  Priestley  dis- 
covered oxygen  is  an  interesting  one,  and  may  be  performed  with  the 
apparatus  shown  in 
Figure  15.  An  or- 
dinary test  -tube  — 
coated  with  cop- 
per by  electro  -  de- 
position for  about 
two  inches  from  the 
sealed  end  —  is  used 
to  contain  the  mer- 
curic oxide,  and  is 
supported  above 
the  gas-burner  by  a 

clamp.      By  means 

„  ITT          Fig.  15.  Preparation  of  Oxvgen  from  Mercuric  Oxide. 

of  a  cork  and  tube, 

the  oxygen  as  evolved  is  conducted  beneath  the  mouth  of  a  glass" 
receiver  filled  with  water,  standing  in  the  porcelain  cistern^  _ 

The  usual  method  of  obtaining  oxygen  is  by  heating  potassium 
chlorate,  when  the  following  reaction  takes  place: 

(KC103)2    :        (KC1)2     +     (02), 

But,  since  this  Decomposition  takes  place  at  a  very  elevated  tempera- 
ture, and  then  witb  almost  explosive  rapidity,  it  is  found  convenient 
in  practice  to  mix  the  salt  with  one  fourth  of  its  weight  of  some 
metallic  oxide,  such  as  ferric  or  cupric  oxide,  or  manganese  di-oxide. 


128 


Fig.  16.  Preparation  of  Oxygen  from  Potas 
Chlorate. 


The  mode  in  which  these  oxides  act  is  not  certainly  known  ;  hut  by 
their  use  the  oxygen  is  evolved  with  great  uniformity  and  at  a  far 
lower  temperature,  though  it  is  not  quite  as  pure.  The  oxide  is  ap- 
parently unchanged  by  the  operation.  The  apparatus  employed  is 

shown  in  Fig.  16.  The1 
mixture  of  potassium 
chlorate  and  mangan- 
ese di-oxide  is  placed 
in  a  tlask  standing  in 
a  sand-bath,  through 
the  cork  of  which  a 
bent  glass  tube  passes 
to  convey  the  oxygen 
as  set  free  -to  the  cyl- 
inder previously  lilled 
with  water  and  stand- 
hig  in  tlie  water-cis- 
tern.  Upon  applying 
heat  the  gas  is  regularly  evolved  and  may  be  collected  for  examina- 
tion over  water  as  shown  in  the  figure,  or,  as  it  is  heavier  than  air,  by 
displacement.  When  larger  quantities  of  the  gas  are  required,  the 
glass  flask  may  be  advantageously  replaced  by  a  conical  flask  with  a 
flat  bottom  made  of  sheet  iron. 

172.  Properties.  —  I.  PHYSICAL.  —  Oxygen  is  a  colorless, 
odorless,  and  tasteless  gas.  It  is  somewhat  denser  than  air, 
its  specific  gravity  being  1-10563.  Water  dissolves  it  slightly, 
100  volumes  at  0°  taking  up  4'1  volumes  of  oxygen.  When 
subjected  to  a  pressure  of  20  atmospheres,  at  a  temperature 
of  —136°  obtained  by  immersing  it  in  boiling  ethylene,  it  is 
condensed  to  a  transparent  liquid  having  a  density  somewhat 
less  than  that  of  water.  Its  critical  temperature  is  —  118° 
and  its  critical  pressure  is  50  atmospheres.  Under  these  con- 
ditions its  density  is  0'65,  which  increases  to  0'87  at  —139° 
and  to  1-124  at  —200°.  The  liquid  oxygen  boils  at  —181° 
under  a  pressure  of  one  atmosphere  and  at  —198°  under 
a  pressure  of  six  millimeters.  Its  expansion-coefficient  at 
—  139°  is  0-01706.  Its  refractive  power  is  to  that  of  air  as 
0-8616  to  1.  li  is  strongly  magnetic  ;  calling  the  magnetism 


PROPERTIES  OF  OXYGEN.  129 

of  iron  1,000,000,  that  of  oxygen  is  377.  Hence  the  mag- 
netic power  of  the  atmospheric  oxygen  is  quite  appreciable, 
being  equal  to  that  of  a  layer  of  iron  covering  the  earth  to 
the  thickness  of  O'l  millimeter.  The  diurnal  variations  of 
the  magnetic  needle  are  supposed  to  be  due,  at  least  par- 
tially, to  variations  in  the  intensity  of  this  magnetism,  owing 
to  changes  of  temperature. 

II.  CHEMICAL. — Oxygen  is  capable  of  entering  into  com- 
bination with  all  the  elements  but  fluorine.  But,  in  the  state 
in  which  it  is  usually  obtained,  an  elevation  of  temperature 
is  necessary  to  bring  about  this  union.  Combustion,  in  the 
ordinary  use  of  that  term,  is  union  with  oxygen,  attended 
with  light  and  heat.  When  hydrogen,  sulphur,  charcoal, 
phosphorus,  sodium,  and  iron,  for  example,  are  brought  in 
contact  with  oxygen  at  a  suitable  temperature,  they  burn, 
evolving  heat  and  light,  and  producing  oxides  of  these  sub- 
stances. Oxygen  is  therefore  an  intensely  active  substance, 
in  which  the  rapidity  of  ordinary  combustion  is  vastly  in- 
creased. It  is  respirable  when  pure,  and  produces  a  quick- 
ening of  the  circulation. 

EXPERIMENTS.  —  A  lighted  candle  burns  far  more  brilliantly  in 
oxygen  than  in  air.  If  it  be  blown  out.  leaving  a  spark  upon  th.e 
wick,  it  is  immediately  rekindled  in  oxygen  gas,  with  a  slight  puft'. 
It  is  by  this  means  indeed  that  this  gas  is  recognized,  a  sliver  of 
wood  with  a  spark  upon  the  end  bursting  into  flame  in  oxygen.  In 
this  way  ajar  filling  with  the  gas  by  displacement  may  be  from  time 
to  time  tested. 

A  piece  of  charcoal — that  from  oak  or  spruce  is  best — having  a 
spark  upon  it,  bursts  into  vivid  combustion  when  placed  in  a  jar 
of  oxygen.  Sulphur,  lighted  and  introduced  in  a  combustion-spoon; 
burns  with  a  bright  blue  flame.  Sodium,  heated  to  redness,  burns 
with  a  dazzling  light.  Iron — used  in  the  form  of  watch  spring  or 
of  small  wire,  to  which  the  end  of  a  match  is  tied — burns  in  oxygen 
with  great  activity. 

The  most  brilliant  experiment  with  oxygen  is  the  combustion  in 
it  of  phosphorus.  A  very  neat  apparatus  for  this  purpose  is  shown 
in  Fig.  17,  A  light  wire  tripod  has  a  ring  at  its  upper  part  for  sup- 


130  lyoituAxir  CHKMISTKY. 


porting  a  globe  to  contain  the  gas,  and  just  below  it  a  shallow  cup, 
containing  water,  into  which  the  neck  of  the  globe  enters.  From  the 
center  of  this  cup  rises  a  wire  crowned  by  a  small 
hemispherical  cup  to  receive  the  phosphorus.  The 
globe  is  filled  about  four  fifths  with  oxygen  by  dis- 
placement, and  is  then  inverted  on  the  stand.  When 
all  is  ready,  a  piece  of  phosphorus  is  cut  from  a 
solid  stick,  and  very  thoroughly  dried  between  sheets 
of  blotting  or  filtering  paper.  The  globe  is  raised, 
the  piece  of  phosphorus  dropped  into  the  cup,  in- 
flamed by  a  hot  wire,  and  the  globe  replaced.  The 
combustion  is  at  once  exceedingly  vivid  ;  but  in  a  few 
seconds  the  phosphorus  becomes  volatilized  by  the 
heat,  and  then  burns  throughout  the  entire  mass  of 
Oxygen.  ^he  oxygen  with  a  brilliance  almost  inconceivable. 

If  now,  after  cooling,  water  be  added  to  the  jars  in  which  these 
combustions  have  occurred,  a  direct  union  will  take  place  between 
the  water  and  the  oxide  produced.  Carbon  produces  carbon  di-oxide; 
sulphur,  sulphurous  oxide;  sodium,  sodium  oxide;  iron,  tri-ferric  tetr- 
oxide;  and  phosphorus,  phosphoric  oxide.  With  water,  the  negative 
oxides  of  carbon,  sulphur,  and  phosphorus  yield  carbonic,  sulphurous, 
and  phosphoric  acids;  and  upon  testing  the  water  with  a  solution  of 
blue  litmus,  it  will  be  found  to  be  reddened.  With  water  the  positive 
oxide  of  sodium  yields  sodium  base,  and  this  turns  a  solution  of  red 
litmus  blue.  The  oxide  of  iron  produced  does  not  form  hydrates,  and 

hence  in  this  jar  the  litmus  is  unaffected. 

* 

173.  Uses.  —  Oxygen  is  used  in  the  arts  for  increasing 
the  intensity  of  combustion,  for  purposes  either  of  heat  or 
light.  Various  methods  have  been  proposed  for  its  manu- 
facture from  the  air  on  the  large  scale,  the  best  of  which 
are:  (1)  Tessie  du  Motay's,  which  consists,  first,  in  passing 
pure  air  over  a  heated  mixture  of  manganese  di-oxide  and 
sodium  hydroxide,  producing  by  its  oxygen  sodium  manga- 
nate  ;  and  second,  in  heating  this  manganate  still  higher,  by 
which,  with  the  aid  of  a  current  of  steam,  it  is  decomposed 
into  the  original  materials  again,  setting  the  oxygen  free. 
(2)  Mallet's,  in  which  cuprous  chloride  is  oxidized  by  pass- 
ing air  over  it  at  a  high  temperature,  to  cupryl  chloride, 


HISTOIfY  OF  <)/,<)\K.  131 

which  at  a  higher  temperature  becomes  cuprous  chloride  and 
oxygen  again.  (3)  Boussingault's,  which  consists  in  passing- 
moist  air  over  heated  barium  oxide,  whereby  it  is  oxidized  to 
barium  peroxide ;  and  then  raising  the  temperature  of  this 
peroxide  to  400°,  by  which  it  is  decomposed  into  barium 
oxide  and  oxygen.  And  (4)  Deville's,  which  consists  in  the 
decomposition  of  sulphuric  acid  by  heat. 

In  the  natural  world,  the  uses  of  oxygen  are  well-nigh 
infinite.  Diluted  with  nitrogen  in  the  air,  it  is  continually 
entering  and  leaving  chemical  combinations,  setting  free  in 
the  former  and  absorbing  in  the  latter  enormous  stores  of 
energy.  It  is  by  the  oxygen  of  respiration  that  the  energy 
of  living  beings  is  set  free  from  their  food ;  it  is  by  the  sep- 
aration again  of  oxygen  by  the  sunlight  that  that  energy  is 
stored  up  anew  in  this  food.  Faraday  has  calculated  that 
6,000,000,000  pounds  of  oxygen  are  daily  consumed  in  the 
respiration  of  animals;  and  that  the  daily  consumption  of 
oxygen  for  all  purposes  whatever  reaches  the  enormous  sum 
of  7,142,857  tons!  We  have  not,  however,  to  fear  an  ex- 
haustion of  the  supply,  since  the  air  of  the  globe,  were  no 
oxygen  added  to  it,  contains  enough  of  this  gas  to  supply 
this  enormous  demand  for  480,000  years. 

OZONE. — Molecular  formula  O.r  Molecular  mass  47 '88.  Molec- 
ular volume  2.  Relative  density  23*94.  The  mass  of  1  liter 
at  0°  is  2-145  grams  (23  '94  criths). 

174.  History. — Oxygen,  like  chlorine,  is  capable  of  ex- 
isting in  both  passive  and  active  states.  The  passive  condi- 
tion is  the  one  we  have  just  considered.  The  active  condi- 
tion is  termed  ozone.  As  early  as  1785,  von  Marum  no- 
ticed that  oxygen,  upon  being  electrified,  acquired  an  odor 
strongly  resembling  that  perceived  after  a  stroke  of  light- 
ning, and  usually  termed  "sulphurous."  It  was  not  until 
1840,  however,  that  any  accurate  experiments  were  made  on 
the  subject.  Then  Schonbein  noticed  the  similarity  between 


132  IXORGAXIC  CHEMTSTRY. 

the  electrical  odor  and  that  produced  in  the  electrolysis  of 
water  and  in  the  slow  oxidation  of  phosphorus  and  of  sul- 
phur ;  and  showed  that  in  each  of  these  cases  the  substance 
produced  turned  paper  moistened  with  a  solution  of  potas- 
sium iodide  and  starch,  to  a  deep  blue.  The  same  year  Ma- 
rig-nac  and  De  la  Rive  proved  this  substance  to  be  modified 
'oxygen.  In  1852,  Becquerel  and  Fremy  showed  that  pure 
oxygen  could  be  entirely  converted  into  ozone.  In  I860, 
Andrews  and  Tait  showed  that  a  contraction  of  volume 
took  place  when  oxygen  became  ozone ;  and  in  the  same 
year  Soret  showed  that  oil  of  turpentine  absorbed  the  entire 
ozone  molecule,  and  in  this  way  determined  its  relative  den- 
sity ;  confirming  his  results  in  1867  by  the  method  of  diffu- 
sion of  gases.  The  same  year  Andrews  suggested  that  the 
substance  in  the  air  which  affected  test-papers  was  ozone. 
175.  Preparation. — Oxygen  may  be  condensed  to  ozone  : 

I.  By  physical  methods  ;  as 

(a)  Heat;   as  when  a  spiral  of  platinum  wire   is  heated 
in  air. 

(b)  Light ;   as  when  essential  oils  become  strongly  ozon- 
ized in  the  sunlight.     Or,  as  when  the  oxygen  set  free  from 
growing  plants  by  sunlight,  contains  ozone. 

( c)  Electricity ;  1st,  by  the  electric  silent  discharge  through 
oxygen;  2d,  in  the  electrolysis  of  water  acidulated  with  sul- 
phuric and  chromic  acids. 

II.  By  the  chemical  process  of  slow  combustion,  and  in 
some  cases,  of  active  combustion  also.     And  by  the  decom- 
position of  barium  peroxide  and  potassium  permanganate  by 
sulphuric  acid. 

EXPERIMENTS. — For  obtaining  ozone  by  the  action  of  the  silent 
electric  discharge,  the  apparatus  of  Siemens  (Fig.  18)  is  the  most  sat- 
isfactory. As  shown  in  the  diagram  above  the  cut,  it  consists  of  an 
inner  and  an  outer  tuhe  of  glass,  the  inner  surface  of  the  inner  tube 
and  the  outer  surface  of  the  outer  tube  being  covered  with  tin-foil. 
Between  the  two  tubes  a  slow  current  of  pure  dry  ami  well  cooled 
oxygen  passes,  while  the  two  metal  surfaces  are  connected  with  an 


PREPARATION  OF  OZOXK. 


133 


active  induction  coil.  In  this  way  15  per  cent  of  the  oxygen  may  be 
converted  into  ozone,  a  far  larger  amount  than  by  any  other  method. 
To  show  the  contraction  in  volume  when  oxygen  is  converted  into 
ozone,  the  oxygen  may  be 
contained  in  a  cylindrical 
bulb  having  a  long,  nar- 
row neck  bent  into  a  U- 
form.  Through  the  walls 
of  the  cylinder  two  plati- 
num wires  pass,  and  in 
the  bend  of  the  U-tube  a 
little  sulphuric  acid  is 


Fig.  18.  Siemeus's  Tube  for  Ozonizing  Oxygen. 


placed.  On  passing  the 
spark  through  the  gas  by 
means  of  the  platinum  wires,  the  oxygen  is  ozonized  and  the  diminu- 
tion in  volume  is  shown  by  the  rise  of  the  sulphuric-acid  column  on 
the  bulb  side  of  the  U-tube.  On  heating  the  bulb  to  290°,  the  ozone 
is  reconverted  into  oxygen  and  the  original  volume  is  restored.  By 
absorbing  the  ozone  by  oil  of  turpentine,  the  volume  of  ozone  pro- 
duced may  be  determined;  and  hence  its  relative  density. 

A  small  flask  half  full  of  oil  of  turpentine,  exposed  freely  to  the 
air  and  full  sunlight  for  many  weeks,  acquires  powerful  ozonizing 
properties.  Sometimes  the  ozone  is  directly  given  up  to  other  bodies; 
but  often  it  is  not  so  surrendered,  except  by  the  intervention  of  a 
third  body,  called  therefore  an  ozone-carrier.  Platinum  sponge  and 


fl 


ferrous   salts  act  as   such  carriers;    and  blood 
corpuscles  are  specially  active. 

To  produce  ozone  by  the  slow  oxidation  of 
phosphorus,  place  in  a  perfectly  clean  and  spa- 
cious gas-jar,  a  piece  of  phosphorus  a  centime- 
ter in  diameter  and  three  or  four  long,  previ- 
ously scraped  clean,  and  pour  in  water  enough 
to  half  cover  it.  The  jar  is  then  loosely  stop- 
pered and  left  to  itself,  at  the  ordinary  tempera- 
ture, for  several  hours.  The  air  in  the  jar  will 
then  be  found  strongly  ozonized. 

To  produce  ozone  by  the  slow  combustion 
of  ether,  a  few  drops  of  ether  are  poured  into  a 
beaker,  as  shown  in  Fig.  19,  across  the  top  of  which  is  placed  a  rod 
on  which  hang  two  slips  of  test-paper,  one  of  blue  litmus  for  acids, 
the  other  for  ozone.  If  now  a  glass  rod,  previously  heated  to  a  high 

'  1Q 


Fig.  19.  Ozone  by  Slow 
Combustion  of  Ether. 


Io4  IXftlKtANIC  CHEMISTRY. 


temperature,  be  thrust  into  the  jar,  the  ether  will  undergo  slow  com- 
bustion, generating  acid-vapors  which  redden  the  litmus  paper,  while 
the  ozone,  which  is  formed  at  the  same  time,  will  turn  the  other  paper 
blue. 

If  a  vigorous  blast  of  air  be  directed  from  a  glass  tube  through 
the  extreme  top  of  the  flame  of  a  Bunsen  gas-burner  into  a  capacious 
beaker,  the  air  in  the  beaker  will  give  the  reaction  for  ozone  ;  an  evi- 
dence that  it  is  produced  in  rapid  combustion. 

176.  Properties.  —  Physically,  ozoiie  is  like  oxygen,  ex- 
cept in  density  ;  it  is  half  as  dense  again  as  that  gas.  When 
ozonized  oxygen  is  cooled  to  —181  '4°  by  placing  it  in  liquid 
oxygen  at  atmospheric  pressure,  ozone  is  easily  obtained  as 
a  dark  blue  liquid,  transparent  in  thin  layers,  but  almost 
opaque  in  a  layer  two  millimeters  thick.  Its  boiling  point  is 
—  106°.  It  yields  a  bluish  gas  on  evaporation,  which  re- 
condenses  on  immersion  in  liquid  ethylene. 

Chemically,  too,  it  is  like  oxygen,  in  the  fact  that  all  its 
compounds  are  oxides.  In  a  word,  it  is  oxygen  with  prop- 
erties intensified  ;  it  is  active  oxygen.  It  has  a  bluish  color 
and  a  strong  odor,  which  is  said  to  resemble  that  of  weak 
chlorine  ;  hence  its  name,  from  o!>,  to  smell.  At  a  temper- 
ature of  290°  it  is  reconverted  into  ordinary  oxygen.  Its 
most  remarkable  property  is  its  powerful  oxidizing  action 
even  at  ordinary  temperatures.  It  bleaches  strongly,  carries 
silver  up  to  the  peroxide,  and  is  very  poisonous  to  animal 
life,  on  account  of  its  irritating  action  upon  the  mucous  sur- 
faces. It  is  soluble  only  in  oil  of  turpentine  or  oil  of  cinna- 
mon. It  decomposes  potassium  iodide,  oxidizing  the  potas- 
sium and  setting  the  iodine  free. 

When  ozone  oxidizes  a  substance,  there  is  no  change  in 
volume,  although  the  ozone  itself  disappears,  the  third  atom 
of  oxygen  alone  entering  into  combination.  The  production 
of  ozone  from  oxygen  is  an  endothermic  reaction  : 

(O2)2  +  O2  =  (O3)2  —  72,400  water-gram  degrees. 
Hence  energy  must  be  added  to  the  oxygen  to  convert  it 


OCCURRENCE  OF  OZONE.  135 

into  ozone ;  the  increased  activity  of  ozone  is  thus  accounted 
for,  as  well  as  its  instability. 

177.  Tests. — Schonbein's  test  consists  of  paper  moistened 
with  a  dilute  solution  of  potassium  iodide  and  starch.     The 
iodine  is  set  free  by  the  ozone,  and  colors  the  starch  deep 
blue.     Fremy's  test  is  paper  moistened  with  an  alcoholic 
tincture  of  guaiacum  ;  it  is  turned  light  blue  by  ozone.     Pa- 
per moistened  with  manganous  sulphate,  or  lead  hydrate,  be- 
comes dark  brown' or  black  in  ozone.     The  most  distinctive 
test  is  metallic  silver,  which  is  converted  by  ozone  into  the 
brown  peroxide. 

EXPERIMENTS. — To  prepare  Schonbein's  test-paper,  one  part  of 
pure  potassium  iodide  is  dissolved  in  two  hundred  parts  of  water,  the 
solution  gently  heated,  ten  parts  of  line  starch  gradually  added,  and 
the  heating  continued  until  the  whole  becomes  homogeneous.  Slips 
of  filtering  paper  are  then  drawn  through  the  solution  and  dried  in 
the  air.  They  must  be  kept  in  a  closely  stoppered  bottle.  When  one 
of  these  slips  is  moistened  and  exposed  to  an  atmosphere  containing 
ozone,  it  becomes  deep  blue.  The  bleaching  action  of  ozone  may  be 
shown  by  agitating  in  a  jar  of  air  ozonized  by  phosphorus  a  little 
very  dilute  solution  of  indigo.  It  is  at  once  decolorized. 

178.  Occurrence  and  Uses. —  Ozone  is  found  free  in 
the  air,  in  small  quantities,  especially  after  a  thunder-storm. 
It  is  also  produced  by  decay,  and  probably  by  plant  growth. 
It  has  been  supposed  to  oxidize  and  destroy  impurities  in  the 
air.     One  volume  of  air  containing  g-oVo  °^  ozoue  will  purify 
540  volumes  of  putrid  air.     On  the  other  hand,  on  account 
of  its  irritating  action  when  breathed,  it  has  been  assumed 
to  be  the  cause  of  influenzas,  etc.     But  in  the  absence  of 
exact  data,  it  is  not  possible  to  decide  whether  atmospheric 
ozone  performs  any  well-defined  function.    In  the  arts  it  has 
been  used  as  a  disinfectant,  and  also  as  a  bleaching  agent. 

It  is  probable  that,  while  the  molecule  of  oxygen  is  diat- 
omic, that  of  ozone  is  triatomic,  thus : 

O  =  O 

0-0 

Oxygen.  Ozone. 


136  JXORUAXIC  CHEMISTRY. 

So  that  while  in  the  case  of  ozone  we  have  another  instance 
of  allotropism — ozone  being  allotropic  oxygen — we  have  here 
an  instance  in  which  the  allotropism  is  evidently  due  to  a  con- 
densation within  the  molecule.  Hence  the  conclusion  seems 
reasonable  that  all  allotropism  may  be  due  to  a  similar  cause. 

COMPOUNDS  OF  OXYGEN  WITH  HYDROGEN. 

HYDROGEN  OXIDE. — Formula  H.,O.  Molecular  mass  17.96. 
Molecular  volume  2.  Relative  density  8*98.  The  maw  of  1 
liter  of  water-vapor  is  0'8064  grams  (8*98  criths).  Specific 
gravity  1.  Solidifies  at  0°.  Boils  at  100°.  Molecular  majs 
in  the  liquid  state  probably  35 '92. 

179.  History.  —  Hydrogen  oxide,  or  water,  was  consid- 
ered to  be  an  elementary  substance  until  1776,  when  Lavoi- 
sier showed  its"  compound  nature.     Cavendish  and  Watt 
in  1781,  first  proved  its  composition  by  synthesis.     In  1805, 
Humboldt  and  Gay-Lussac  ascertained  that  the  ratio  of 
its  constituents  by  volume  is  as  2  :  1 ;  and  Berzelius  and 
Dulong-  proved  that  the  mass-ratio  is  as  1  :  8. 

180.  Occurrence. — Water  occurs  abundantly  diffused  in 
nature,  both  free  and  in  combination.     Natural  waters  are 
seldom  pure ;    even  the  water  which  falls  as  rain  contains 
atmospheric  impurities  to  an  extent  of  3  per  cent  or  more. 
It  is  essential  to  the  life  of  plants  and  animals,  and  enters 
into  the  composition  of  many  mineral  substances.      Seven 
eighths  of  the  entire  human  body  is  water. 

181.  Preparation. — Hydrogen  oxide  may  be  prepared 
synthetically ;  that  is,  by  the  direct  union  of  its  constituent 
elements.     The  product  of  the  combustion  of  hydrogen  is 
always  water,  as  we  have  seen.     (Fig.  6.)    And  when  the 
two  gases  are  mixed  together  in  the  ratio  of  two  volumes 
of  hydrogen  to  one  of  oxygen,  they  may  be  caused  to  unite 
by  a  flame,  by  an  electric  spark,  or  by  finely  divided  plati- 
num.   The  heat  evolved  by  their  union  is  very  great ;  when 


HYDROGEN  OXIDE. 


137 


the  two  gases  are  burned  together  in  the  above  proportions 
from  a  jet,  they  give  the  most  intense  heat  which  can  be  ob- 
tained by  combustion.  This  experiment  was  first  made  by 
Hare,  of  Philadelphia,  in  1801 ;  and  the  apparatus  is  called 
the  compound  or  oxy-hydrogen  blowpipe. 

EXPERIMENTS. — To  show  the  production  of  water  by  the  combus- 
tion of  hydrogen,  the  experiment  described  under  hydrogen  may  be 
repeated.  In  Fourcroy's  exper- 
iment the  gas  continued  to  burn 
for  a  week,  consuming  37,500 
cubic  inches  of  oxygen  and  hy- 
drogen and  producing  15  ounces 
of  pure  water. 

To  show  the  union  of  the 
mixed  gases  by  flame,  a  mass 
of  soap-bubbles  may  be  blown 
in  a  metallic  dish  containing 
soap  and  water,  by  a  bubble- 
pipe  attached  to  a  gas-bag  con- 
taining one  volume  of  oxygen 
to  two  of  hydrogen.  On  apply- 
ing a  flame  (Fig.  21)  the  gnses 
explode  with  a  loud  report. 

For  the  purpose  of  measuring  exactly  the  proportions  in  which  the 
gases  unite,  an  instrument  called  a  eudiometer  is  employed. 

Fig.  22  represents  the  form  proposed  by  Ure;  it  is  simply  a  U- 

shaped  tube  of  glass  which 
is  closed  at  one  end,  the 
closed  limb  being  gradu- 
ated, and  pierced  near  its 
extremity  by  two  platinum 
wires.  This  limb  is  to  be 
filled  with  water,  and  then 
a  given  quantity  of  pure 
oxygen,  say  20  cubic  centi- 
Fig.  21.  Explosion  of  mixed  Oxygen  and  Hy-  meters  is  to  be  introduced 
drogen gases.  from  a  delivery-tube;  50 

cubic  centimeters  of  hydrogen  are  then  similarly  introduced  —  all 
measurements  being  made  when  the  level  of  the  liquid  is  the  same  in 


Fig.  20.  Water  from  the  combustion  of 
Hydrogen. 


138 


both  limbs  —  the  open  end  is  closed  firmly  by  the  thumb,  as  shown 
in  the  figure — a  cushion  of  air  being  left  between  it  and  the  liquid  - 
and  a  spark  passed  through  the  mixed  gases  by 
means  of  the  platinum  wires.  Upon  restoring 
the  level  of  the  liquid  by  adding  water,  10  cu- 
bic centimeters  of  gas  will  be  left,  which,  on 
examination,  will  be  found  to  be  pure  hydrogen. 
Hence  20  volumes  of  oxygen  have  united  with 
40  of  hydrogen  to  form  water.  But  this  is  the 
ratio  of  1  :  "2,  which  theory  requires. 

The  remarkable  action  of  spongy  platinum 
in  causing  the  union  of  oxygen  and  hydrogen 
Pig.  22.  lire's  Eudiom-    gases,  may  be  shown  by  holding  a  piece  of  this 
metal — or  what  answers  equally  well,  a  piece  of 

asbestus  previously  moistened  with  strong  platinic  chloride  solution 
and  heated  to  redness — over  a  jet  from  which  hydrogen  is  issuing. 
The  mass  becomes  at  once  red-hot  and  fires  the  gas.  This  effect  is 
attributed  to  the  enormous  surface-attraction  which  platinum,  in  this 
form,  has  for  gaseous  substances.  Exposed  to  the  air,  platinum-sponge 
condenses  oxygen  in  this  way  within  it,  perhaps  to  the  state  of  a  liquid. 
When  now  it  is  exposed  to  hydrogen,  it  condenses  this  gas  also;  thus 
bringing  them  together  and  causing  their  union. 

The  great  heat  evolved  by  burning  oxygen  and  hydrogen  gases 
together  requires  for  its  production  a  concentric  jet,  consisting  of  an 
inner  tube  carrying  the  oxygen,  and  outside  of  this  a  second  tube  be- 
tween which  and  the  first  the  hydrogen  passes.  The  two  gases  must 
be  brought  from  separate  gas-holders.  The  hydrogen  is  first  lighted; 
it  burns  with  a  large  yet  pale  flame.  On  admitting  the  oxygen,  this 
flame  becomes  smaller,  and  is  drawn  out  very  long  and  fine,  being 
altered  also  in  color.  If  this  flame  be  directed  upon  various  metals 
contained  in  small  cups  of  charcoal,  they  may  be  melted  and  burned, 
each  with  its  characteristic  color.  The  brilliance  of  the  experiment 
is  much  heightened,  in  many  cases,  by  shutting  off  the  hydrogen  and 
allowing  the  combustion  to  take  place  in  the  oxygen  alone.  A  watch- 
spring  or  a  smalt  file,  introduced  into  the  flame,  burns  with  vivid 
scintillations.  A  piece  of  cast-iron  on  charcoal  gives,  after  melting 
it  and  shutting  off  the  hydrogen,  a  superb  pyrotechnical  effect.  On 
introducing  some  infusible  substance,  as  a  pipe-stem,  a  cylinder  of 
magnesia  or  zirconia,  or  still  better,  one  of  lime,  the  light  emitted  is 
dazzling.  This  light  was  first  utilized  practically  in  the  trigonomet- 
rical survey  of  Great  Britain,  by  Lieut.  Drummond,  when  it  was  seen 


ANALYSIS  OF  WATER. 


139 


108  miles  in  full  daylight.  It  is  sometimes  called  the  Drummond 
light;  but  is  more  properly  called  the  calcium  or  oxy-hydrogen  light. 
By  means  of  an  oxy-hydrogen  flame  3,200  ounces  of  platinum  have 
been  melted  in  one  operation. 

But  not  only  may  the  composition  of  water  be  established 
by  synthesis,  it  may  be  equally  well  determined  by  analysis. 
For  this  purpose  both  direct  and  indirect  means  may  be  em- 
ployed. 

EXPERIMENTS. — In  the  sodium  experiment  (Fig.  1)  the  hydrogen 
set  free  must  have  been  derived  from  the  water  on  which  the  sodium 
acted.  If  a  little  solution  of  red  litmus  be  added  to  the  water  after 
the  experiment,  it  will  be  blued.  A  base  must  therefore  have  been 
produced  by  the  sodium;  but  a  base  contains  oxygen,  which  oxygen 
must  also  have  come  from  the  water.  In  this  way 
the  composition  of  water  may  be  established  by 
an  indirect  analysis. 

To  analyze  water  directly,  it  may  be  submitted 
to  the  action  of  electricity.  But  as  water  itself  is 
not  decomposed  by  this  agent,  a  secondary  action 
must  be  made  use  of.  A  little  sulphuric  acid  is 
added  to  the  water ;  this  is  decomposed  by  the  elec- 
tric current,  and  reacts  upon  the  water,  separating 
it  into  its  constituents.  A  convenient  apparatus 
for  this  purpose  is  shown  in  Fig.  28.  Two  tubes 
closed  at  one  end  and  filled  with  water  are 
suspended  with  their  mouths  beneath  the 
surface  of  some  acidulated  water  contained 
in  the  glass  dish  below.  Through  the 
sides  of  this  dish  two  wires  pass,  each 
terminating  in  a  plate  of  platinum  seen 
beneath  the  open  ends  of  the  tubes.  On 
connecting  these  wires  with  a  Bunsen's  or  Grove's  battery  of  6  or  8 
cells,  a  torrent  of  gas-bubbles  rises  from  each  platinum  plate  into  the 
tube  placed  above  it.  It  will  soon  be  noticed  that  the  tube  over  the 
negative  electrode  fills  twice  as  rapidly  as  the  other;  and  on  testing 
the  gas  in  each,  when  the  tubes  are  both  full,  the  gas  in  this  tube  will 
be  found  to  be  hydrogen,  while  that  in  the  other  is  oxygen.  Water 
contains  therefore  2  volumes  of  hydrogen  and  1  volume  of  oxygen. 
And  as  the  mass  of  oxygen  is  16  times  that  of  hydrogen,  the  mass- 


Fig.  23.  Decomposition  of 
Water  by  Electricity. 


140 

ratio  must  be  as  2  :  16  or  as  1  :  8;  or  more  exactly,  water  consists  of 
of  88-89  per  cent  of  oxygen  and  11-11  per  cent  of  hydrogen. 

182.  Properties. — Hydrogen  oxide  is  a  limpid  liquid, 
without  odor  or  taste.  lu  thiu  layers  it  is  colorless,  but  in 
thick  layers  it  is  distinctly  blue.  It  is  neither  acid  nor  alka- 
line in  its  action  upon  vegetable  colors,  is  a  poor  conductor 
of  heat  and  a  non-conductor  of  electricity.  It  is  773  times 
heavier  than  air  at  0°.  It  is  the  standard  of  specific  gravity 
for  liquids,  and  is  taken  as  the  unit  of  mass  in  the  decimal 
system,  the  mass  of  one  cubic  centimeter  of  water  at  4° 
being  1  gram ;  hence  the  mass  of  one  liter  of  water  at  the 
same  temperature  is  1  kilogram.  When  cooled  to  0°,  it  solid- 
ifies in  crystals  which  are  derived  from  the  hexagonal  prism, 
and  which  are  often  very  beautifully  seen  in  snow-flakes, 
Fig.  24.  The  melting-point  of  ice  is  lowered  by  '0075°  for 


Fig.  24.  Snow  Crystals. 

every  atmosphere  increase  of  pressure.  When  heated  to 
100°  under  atmospheric  pressure  it  is  converted  into  vapor 
called  steam.  The  rate  of  its  expansion  by  heat  increases 
slightly  with  the  temperature ;  though  at  4°  water  reaches 
its  point  of  maximum  density,  and  then,  if  cooled  below  this, 
it  expands  until  its  solidifying  point  is  reached.  At  the 
moment  of  becoming  solid  it  increases  considerably  in  vol- 
ume, 916  cubic  centimeters  of  water  becoming  1,000  of  ice. 
Its  index  of  refraction  at  0°  is  1'333.  It  is  also  the  stand- 
ard of  specific  heat,  since  it  requires  more  heat  to  raise  its 
temperature  a  given  number  of  degrees  than  any  other  solid 
or  liquid.  In  the  form  of  steam  it  is  a  colorless  gas,  having 
a  relative  density  of  8 '98,  or  a  specific  gravity  of  0-622,  air 


CHEMICAL  rUOPEKTIES  OF  WATER.  141 

being  1.  One  volume  of  water  yields  1,696  volumes  of  steam 
at  100°.  The  heat  of  liquefaction  of  water  is  80-025  heat- 
units.  The  heat  of  vaporization  is  536 '5  heat-units.  The 
critical  temperature  is  370°,  and  the  critical  pressure  195 '5 
atmospheres. 

Chemically,  water  is  a  very  active  substance.  It  enters 
into  combination  directly  with  most  positive  and  negative 
oxides,  forming  bases  with  the  former  and  acids  with  the 
latter,  evolving  more  or  less  heat.  A  familiar  example  of 
this  is  the  slaking  of  lime,  a  process  which  may  be  repre- 
sented by  the  following  equation  : 

CaO     +     H20     =     Ca"(OH)2 

Calcium  oxide.         Water.  Calcium  hydroxide. 

Water  also  enters  molecularly  into  the  composition  of 
many  crystalline  substances,  the  amount  appearing  to  in- 
crease in  proportion  as  the  crystallization  takes  place  in  a 
colder  and  more  dilute  solution.  Calcium  sulphate  crystal- 
lized takes  two  molecules,  CaSO,,  2  aq. ;  copper  sulphate, 
five,  CuSO4,  5  aq. ;  magnesium  sulphate,  seven,  MgSO4,  7 
aq. ;  sodium  sulphate,  ten,  Na.,SO4,  10  aq. ;  and  potassio- 
aluminic  sulphate  (alum),  twelve,  KA1(SO4)2,  12  aq.  Such 
crystals,  when  exposed  to  dry  air,  effloresce;  i.  e.,  lose  this 
water  of  crystallization  and  fall  into  a  white  powder.  On 
the  other  hand,  some  substances,  in  a  moist  atmosphere, 
attract  water  and  liquefy :  this  is  called  deliquescence.  The 
solvent  power  of  water  is  very  much  greater  than  that  of 
any  other  liquid.  Each  substance  which  it  dissolves,  how- 
ever, has  a  fixed  limit  of  solubility,  which  depends  upon 
temperature,  etc.  Gaseous  solubility  is  to  a  very  large  ex- 
tent dependent  upon  atmospheric  pressure  also.  Water  is 
obtained  pure  and  free  from  dissolved  foreign  substances 
only  by  distillation. 

When  water-vapor  is  produced  from  its  constituent  gases 
without  change  of  volume  the  synthetical  reaction  is 
(H,)2  +  O2  =  (H,O).2  -f  114,320  water-gram  degrees; 


142  'INORU.IMC  < 'II  KM  I  WHY. 

and  hence  water  is  highly  exothermic  and  proportionately 
stable.  When  the  water  is  obtained  as  a  liquid  each  gram 
of  hydrogen  burned  evolves  34,180  heat-units.  Conversely 
the  decomposition  of  water  is  endothermic  and  requires  this 
quantity  of  heat  to  be  furnished  from  without.  The  disso- 
ciation of  water  is  effected  at  1000°  and  is  half  completed 
at  2500°.  Moreover,  heat-changes  also  accompany  the  act 
of  solution.  Thus  the  solution  of  KC1,  KBr  and  KI  in 
water  absorbs  4,440,  5,080,  and  5,110  units  of  heat  respect- 
ively; while  the  solution  of  Nal  evolves  1,220,  that  of 
BaBr2  evolves  4,980,  that  of  LiCl  8,440,  that  of  Na2P2O7 
11,850,  and  that  of  KOH  13,290  heat-units,  according  to 
Thomsen. 

183.  Natural  Waters. — The  purest  natural  water  which 
can  be  obtained  is  that  which  falls  as  rain ;  but  even  this  is 
contaminated  with  matters  washed  from  the  air.  Other  nat- 
ural waters  may  be  divided  into  potable  (or  drinkable),  min- 
eral, and  saline  waters.  Of  potable  waters,  river  and  lake 
waters,  especially  such  as  are  found  in  granite  regions,  are 
the  purest.  That  of  Loch  Katrine  in  Scotland,  containing 
but  2  grains  of  solid  matter  to  the  gallon,  is  one  of  the 
purest  waters  known;  while  the  purest  water  supplied  to 
any  city  in  this  country  is  that  from  Lake  Cochituate  which 
supplies  Boston,  which  contains  but  3*11  grains  in  one  gal- 
lon. The  Schuylkill  water  (Philadelphia)  contains  3  •  50 
grains  ;  Ridge  wood  (Brooklyn)  3 '92  ;  the  Croton  (New  York) 
4-78;  Lake  Michigan  (Chicago)  6'68;  the  water  which  sup- 
plies Albany,  10-78 ;  and  that  of  the  Thames,  which  supplies 
London  in  part,  16'38  grains,  in  each  gallon.  Spring  and 
well  waters  are  seldom  as  pure  as  surface  waters,  since  they 
have  penetrated  the  ground  and  taken  up  solid  impurities. 
Thus  the  water  of  a  well  near  Central  Park,  New  York, 
gave  43*54  grains;  one  in  Schenectady,  49*21  grains;  one 
in  Amsterdam,  69.93  grains ;  and  one  in  London,  99'97  grains 
of  solid  matter  to  the  gallon.  Mineral  waters  are  classified, 


//  YDifoa  /<:.y  rKHoxiDK.  1 43 

according  to  their  prevailing  constituents,  into  sulphurous, 
chalybeate,  alkaline,  etc.  The  amount  of  solid  matters  which 
they  hold  in  solution  varies  very  widely;  the  chalybeate 
spring  of  Tunbridge  Wells  contains  but  7  grains  to  the  gal- 
lon, while  the  Saratoga  Seltzer  spring  contains  over  400,  one 
of  the  springs  at  Vichy,  460,  the  High  Rock  spring  at  Sara- 
toga, 628,  and  the  artesian  Lithia  spring  at  Ballston,  1,233. 
Saline  waters,  especially  those  of  inland  lakes  with  no  outlet, 
are  most  impure.  Sea-water  contains  on  an  average,  2,500 
grains  of  solid  matter,  the  water  of  the  Dead  Sea  12,600 
grains,  and  that  of  the  Great  Salt  Lake  22,000  grains  to  the 
gallon. 

Water  for  drinking  should  be  as  pure  as  it  is  possible  to 
obtain  it.  Indeed,  in  some  of  our  cities  distilled  water  prop- 
erly aerated  is  sold  for  table  use.  The  effervescent  table  wa- 
ters now  largely  used  are  of  value  in  proportion  as  the  water 
of  which  they  are  made  is  pure.  The  most  serious  contami- 
nation of  water  is  that  arising  from  sewage,  coining  either 
from  surface  drainage  or  from  soakage  through  the  soil. 
The  greatest  care  should  therefore  be  exercised  in  selecting 
a  source  of  water  supply,  to  see  that  no  such  cause  of  impu- 
rity exists. 

HYDROGEN  PEROXIDE.  —  Free  hydroxyl.  Formula  H.,Or 
Graphic  H— O— O— H.  Molecular  mass  33'92.  Specific 
gravity  of  liquid,  1*452. 

184.  History. — Hydrogen  peroxide  was  discovered  by 
Thenard  in  1818,  and  called  by  him  oxygenated  water. 

185.  Preparation  and  Properties. — It  is  always  pre- 
pared from  barium  peroxide  by  the  action  of  hydrochloric, 
or,  better,  of  carbonic  acid.     The  reaction  is  : 

BaO,  +  H2COS  =  BaCO,  +   H,O2 

By  adding  the  materials  alternately,  the  water  present  soon 
becomes  saturated ;  then,  by  evaporation  over  sulphuric  acid, 


144  IXORGAXIC  C 

this  water  may  be  removed,  thus  leaving  pure  hydrogen  per- 
oxide. 

It  is  always  formed  by  slow  oxidation  in  presence  of  moist- 
ure ;  the  hydrogen  peroxide  thus  produced  being  detected  in 
the  liquid  by  proper  means.  It  would  appear  that  its  pro- 
duction under  these  conditions  is  to  be  viewed  not  as  an  oxi- 
dation of  water,  but  rather  as  due  to  the  action  of  nascent 
hydrogen  upon  oxygen.  (Traube.)  If  air  or  oxygen  be  passed 
through  acidulated  water  undergoing  electrolysis,  hydrogen 
peroxide  appears  at  the  negative  or  hydrogen  electrode. 

Hydrogen  peroxide  is  a  colorless  syrupy  liquid,  of  spe- 
cific gravity  1'452.  It  does  not  solidify  at  —30°,  and  may 
be  evaporated  in  vacuo  unchanged.  It  begins  to  decompose 
at  15°,  and  at  100°  it  separates  into  water  and  oxygen  with 
almost  explosive  violence.  It  is  more  permanent  if  diluted 
with  water.  It  has  a  harsh  taste,  and  whitens  the  skin  when 
placed  upon  it.  It  bleaches  vegetable  colors. 

Hydrogen  peroxide,  as  already  mentioned  (page  77),  is  an 
endothermic  compound,  being  formed  with  the  absorption 
of  energy: 

(H2O)2  +  O2  =  (H,O2)2—  44,000  water-gram  degrees. 

Its  activity  is  seen  to  be  due  to  the  increased  amount  of  en- 
ergy it  contains  over  that  existing  in  water.  Moreover  to 
this  cause  is  due  its  instability  also. 

Its  most  remarkable  property  is  the  facility  with  which  it 
evolves  oxygen  under  certain  conditions.  It  oxidizes  sele- 
nium, chromium  and  arsenic,  converts  lead  sulphide  into  sul- 
phate, and  sets  free  iodine  from  hydrogen  iodide.  Metallic 
platinum,  gold,  and  silver,  when  finely  divided,  decompose 
it  almost  with  explosion ;  their  oxides,  as  well  as  the  perox- 
ides of  lead  and  manganese,  also  decompose  it,  giving  up  a 
part  of  their  oxygen  at  the  same  time.  Ozone  is  decomposed 
by  it,  water  and  oxygen  being  the  sole  products.  It  is  there- 
fore at  once  an  oxidizing  and  reducing  agent.  The  similarity 


OX1DKH  AM)  ACIDS  OF  CHLORINE.  145 

in  its  chemical  properties  to  those  of  ozone  arises  doubtless 
from  the  slight  attraction  between  one  of  the  atoms  of  oxy- 
gen and  the  rest  of  the  molecule. 

EXPERIMENTS.  —  The  water  surrounding  the  phosphorus  in  the 
preparation  of  ozone  (p.  133)  contains  hydrogen  peroxide,  and  will 
reduce  a  dilute  solution  of  potassium  permanganate,  itself  a  strong 
oxidizing  agent.  If  to  a  solution  containing  hydrogen  peroxide,  a 
few  drops  of  a  dilute  solution  of  potassium  chromate  be  added,  and 
the  whole  be  agitated  with  ether,  the  ethereal  layer  which  forms  above 
the  liquid  on  standing  will  be  blue  from  the  presence  of  perchromic 
acid.  It  turns  Schonbein's  test-paper  blue,  and  also  blues  guaiacum 
paper.  Indigo  is  also  decolorized  by  it.  These  reactions  are  not  as 
promptly  produced  by  hydrogen  peroxide  as  they  are  by  ozone,  un- 
less a  minute  quantity  of  some  carrier,  such  as  ferrous  sulphate,  be 
present. 

Hydrogen  peroxide  exists  in  small  quantity  in  the  air  and 
may  very  readily  be  detected  in  freshly  fallen  rain-water  or 
snow.  Its  quantity  varies  from  one  twentieth  of  a  milligram 
to  one  milligram  in  a  liter.  The  close  similarity  between  its 
reactions  and  those  of  ozone  causes  the  one  to  be  frequently 
mistaken  for  the  other. 

OXIDES    AND    ACIDS    OF    CHLORINE. 

186.  The  element  chlorine,  as  already  mentioned,  may  act 
as  a  monad,  a  triad,  a  pentad,  or  a  heptad.     Its  oxygen  com- 
pounds, together  with  their  corresponding  hydrates  or  acids, 
are  therefore  as  follows  : 

Hypochlorous  oxide  C1'2O  Hypochlorous  acid  HCl'O 

Chlorous  oxide  C1'"2O3  Chlorous  acid  HCl^O, 

Chloric  oxide  C1V265  Chloric  acid  HC1VQ3 

Perchloric  oxide  Civn.,0.  Perchloric  acid  HC1VIIO4 

Of  these  oxides,  only  the  first  two  have  been  prepared. 
Of  the  acids,  all  have  been  obtained. 

187.  Hypochlorous  Oxide  and  Acid. — Hypochlorous 
oxide  was  discovered  by  Balard  in  1834.     It  may  be  pre- 
pared by  passing  dry  chlorine  gas  over  mercuric  oxide : 

HgO  +   C14  =  HgCl2  +  C1,O 


146  IXOI:<;AM<   CH 

A  yellow  gas,  of  relative  density  43*5,  is  obtained,  which 
condenses  to  a  blood-red  liquid  at  0°.  This  gas  has  a  pene- 
trating, chlorine-like  odor,  and  is  decomposed  with  explosion 
by  very  slight  causes,  yielding  two  volumes  of  chlorine  and 
one  of  oxygen.  It  is  very  soluble  in  water,  uniting  with  it 
to  form  hypochlorous  acid,  Cl(OH),  which  retains  the  odor 
of  the  oxide  and  is  a  powerful  bleaching  agent,  twice  as 
active  as  chlorine. 

Hypochlorites  are  prepared  in  the  arts  by  exposing  alkali 
hydroxides  to  the  action  of  chlorine  gas.  With  sodium  hy- 
droxide, the  reaction  which  takes  place  is  as  follows : 

(HNaO),  +  Cl,  =  NaCIO  +  NaCl  +  H2O 

By  treating  a  hypochlorite  with  dilute  nitric  acid  and 
distilling,  hypochlorous  acid  may  be  obtained. 

HypocKlorites  are  used  very  largely  in  the  arts  as  bleach- 
ing agents;  the  so-called  chloride  of  lime,  a  compound  of 
calcium  chloride  and  calcium  hypochlorite,  being  manufact- 
ured for  this  purpose  on  an  immense  scale. 

188.  Chlorous  Oxide  and  Acid. — Chlorous  oxide  was 
first  described  by  Millon.     It  Is  prepared  by  acting  upon  a 
chlorate  with  nitric  acid  in  presence  of  a  reducing  agent, 
like  arsenous  oxide.     It  is  a  yellowish -green  gas,  having  a 
specific  gravity  of  2*65,  bleaching  indigo  and  litmus,  and 
soluble  in  one  sixth  its  volume  of  water,  forming  chlorous 
acid.     It  is  condensed  to  a  liquid  by  a  cold  of  —20°.     It  ex- 
plodes when  heated  to  57°,  and  also  when  brought  in  contact 
with  sulphur,  phosphorus,  or  arsenic. 

Chlorous  acid,  CIO(OH),  combines  slowly  with  bases,  form- 
ing chlorites,  which  are  unstable,  breaking  up  easily  into 
chlorates  and  chlorides. 

189.  Chlorine  Tetr-oxide.— C1,O,  or  O,Clv-O-Cr"'O. 
This   oxide   is   intermediate  between  chlorous   and   chloric 
oxides,  and  is  decomposed  by  water  and  the  alkalies  into 
chlorous  and  chloric  acids.     It  was  discovered  by  Davy,  in 


CHLOUIC  ACID.  147 

1814,  and  is  obtained  by  the  action  of  sulphuric  acid  upon 
potassium  chlorate,  at  a  low  temperature.  A  dark-greenish 
gas  is  evolved,  which,  strongly  diluted,  has  a  sweetish  aro- 
matic odor,  and  is  strongly  oxidizing  in  its  action.  At  — 20° 
it  condenses  to  an  orange-red  liquid.  It  explodes  with  great 
violence  above  60°,  often  spontaneously. 

EXPERIMENTS.— The  vigor  of  its  action  on  combustibles  may  be 
shown  by  mixing  together  on  a  sheet  of  paper  about  a  gram  of  finely 
pulverized  potassium  chlorate  and  and  an  equal 
quantity  of  fine  sugar.  Place  the  mixture  on  a 
fragment  of  brick,  and  touch  it  with  a  glass  rod 
previously  dipped  in  sulphuric  acid.  The  chlo- 
rine tetr-oxide  thus  set  free  causes  a  vivid  com- 
bustion of  the  entire  mass. 

Or,  a  gram  of  chlorate  in  crystals  may  be 
placed  at  the  bottom  of  a  conical  glass  filled 
with  water  (Fig.  25),  a  few  small  pieces  of  phos- 
phorus   added,  and   sulphuric   acid  allowed  to      Phosphorus^y  (Jhlo- 
come  in  contact  with  the  salt,  by  means  of  a  rine  tetr-oxide. 

pipette.  The  phosphorus  at  once  takes  fire  in  the  chlorine  tetr-oxide 
gas  evolved,  and  burns  vividly. 

19O.  Chloric  Acid.— Chloric  acid,  C1O2(OH),  was  first 
prepared  by  G-ay-Lussac.  On  passing  chlorine  through  a 
solution  of  potassium  hydroxide,  potassium  chlorate  and  po- 
tassium chloride  are  obtained,  according  to  the  equation : 

(0,),  +  (HKO).  =  KC103  +  (KC1).  +  (H,,0)3 

By  adding  to  a  solution  of  potassium  chlorate,  fluo- silicic 
acid,  or  to  one  of  barium  chlorate,  sulphuric  acid,  the  potas- 
sium or  barium  is  separated,  and  there  is  left  an  aqueous 
solution  of  chloric  acid,  which  by  concentration  in  vacuo 
may  be  obtained  as  a  colorless,  syrupy,  acid  liquid,  of  spe- 
cific gravity  1 '28,  and  containing  about  40  per  cent  of  HC1O. , 
which  decomposes  above  40°,  and  is  a  strongly  oxidizing 
agent.  Sulphur,  phosphorus,  alcohol,  paper,  are  at  once  in- 
flamed by  it.  Its  salts,  the  chlorates,  are  also  active  oxidiz- 


148  IXOHGAXIC  Ct/EM/sr/fV. 

ing  agents.  They  are  used  for  the  preparation  of  oxygen, 
and  in  detonating  and  pyrotechuical  mixtures. 

EXPERIMENTS. — Mix  carefully  on  paper  half  a  gram  of  fine  potas- 
sium chlorate  with  quarter  of  a  grain  of  sulphur.  Wrap  up  the  mass 
in  paper,  place  it  on  an  anvil  and  strike  it  with  a  hammer.  It  will 
explode  violently.  Many  new  explosives  have  been  recently  pro- 
posed, consisting  of  potassium  chlorate  mixed  with  tannin,  with  cate- 
chu, and  with  potassium  ferrocyanide  and  sugar.  They  are  all  more 
or  less  unstable  and  therefore  dangerous.  A  mixture  of  amorphous 
phosphorus  and  potassium  chlorate  sometimes  detonates  spontane- 
ously. 

191.  Perchloric  Acid.— Perchloric  acid,  C1O3(OH),  was 

discovered  by  Stadion  in  1815 ;  it  has  been  recently  more 
fully  examined  by  Roscoe.  On  subjecting  potassium  chlo- 
rate to  heat,  it  becomes  pasty  at  a  certain  stage  of  the  proc- 
ess, and  ceases  to  evolve  oxygen..  It  is  then  a  mixture  of 
potassium  perchlorate  and  chloride,  thus : 

(KC1O3)2  =  KC1O4  +  KC1  -f  03 

By  crystallization  the  difficultly  -  soluble  perchlorate  is  ob- 
tained pure ;  and  by  distilling  this  with  sulphuric  acid,  a 
colorless  fuming  liquid  condenses  in  the  receiver,  having  a 
specific  gravity  of  1*782  at  15°.  It  does  not  solidify  at 
— 35°.  This  acid  is  a  powerful  oxidizer  ;  it  instantly  ignites 
wood  or  paper  when  thrown  upon  it,  and  is  decomposed  by 
charcoal,  with  explosion.  It  is  the  most  stable  of  the  chlo- 
rine acids. 

OXIDES    AND   ACIDS    OF   BROMINE   AND    IODINE. 

192.  The  analogy  of  bromine  and  iodine  to  chlorine  is 
shown  also  in  the  similarity  of  their  oxides  and  acids  to 
those  of  that  element.     Theoretically,  the  series  is  the  same, 
though  only  a  few  members  of  it  have  as  yet  been  obtained. 
Of  the  bromine  compounds,  only  the  following  are  known : 

Hypobromous  acid HBr'O 

Bromic  acid 
Perbromic  acid 


XfK  or  s LLPH UR.  1 49 

and  of  those  of  iodine,  only  those  given  below  have  been 

prepared : 

Hypoiodous  acid  HI'O 

lodie  oxide          K2O5  lodic  acid  HIVO3 

Periodic  oxide     IVIIO  Periodic  acid 


193.  lodic  Acid. — lodic  acid  is  the  most  important  of 
the  bodies  given  above.     It  is  prepared  by  the  direct  action 
of  oxidizing  agents  upon  iodine,  or  by  the  simultaneous  ac- 
tion of  chlorine  and  iodine  upon  water : 

I,  +  (C1,)B  4  (H20)6  =  (HIOs)a  +  (HC1)10 
lodic  acid  is  a  colorless  solid,  of  specific  gravity  4*63,  crys- 
tallizing in  ortho-rhombic  prisms;   at  170°  it  loses  a  mole- 
cule of  water,  and  becomes  iodic  oxide. 

§  2.    SULPHUR. 

Symbol  S.  Atomic  mass  31-98.  Valence  II,  IV,  VI.  Rela- 
tive density  of  vapor  31*98.  Molecular  mass  63 '96.  Molec- 
ular volume  2.  Specific  gravity  of  solid  2-04.  The  mass  of 
1  liter  of  sulphur  vapor  at  a  temperature  of  1000°  is  2 '86 
grams  (31*98  criths). 

194.  History.  —  Sulphur  has  been  known  from  the  re- 
motest times. 

195.  Occurrence. — It  is  found  free  in  many  volcanic 
regions,  especially  in  Italy  and  Sicily.      It  occurs  also  in 
combination,  as  a  constituent  of  both  binary  and  ternary 
compounds.     The  sulphides  of  iron,  copper,  lead,  zinc,  anti- 
mony, arsenic,  and  mercury,  are  well-known  minerals ;   as 
tire  also  the  sulphates  of  calcium,  barium,  strontium,  mag- 
nesium, and  sodium.     It  forms  an  essential  part  of  animal 
tissues  and  exists  to  a  considerable  extent  in  those  of  vege- 
tables.    Its  compounds  cause  the  peculiar  odor  of  crucifer- 
ous and  alliaceous  plants,  such  as  mustard  and  garlic. 

Sicily  and  Italy  yield  annually  80,000  tons  of  sulphur, 
•    '  11 


150 


ISOEdA XK'  CHEMISTRY. 


198.  Preparation. — The  sulphur  of  commerce  is  the 
native  material  purified.  As  found,  it  is  mixed  with  vari- 
ous earthy  impurities ;  and  to  separate  it  from  these  it  is 
subjected  to  heat  in  earthen  pots,  as  shown  in  Fig.  2b'. 

These  pots  are  arranged  in  the  furnace  in  two  rows,  and 
are  charged  from  the  top.  The.  sulphur  is  converted  into 
vapor  by  the  heat,  passes  through  the  narrow  tubes  into  a 
second  row  of  earthen  vessels  which  act  as  receivers,  is  there 
condensed  to  a  liquid,  and  runs  out  at  the  bottom  into  wood- 
en vessels  filled  with  water,  placed  below.  Richer  masses  are 


Distillation  of  Sulphur. 


often  heated  in  heaps  with  just  fuel  enough  to  melt  the  sul- 
phur, which  collects  in  a  depression  made  at  the  bottom  of 
the  heap.  The  sulphur  thus  prepared  contains  still  three 
or  four  per  cent  of  impurities  ;  it  is  still  further  refined  by 
another  distillation  in  cylinders  of  iron,  as  shown  in  Fig.  27. 
The  crude  sulphur  is  melted  in  a  tank  by  the  waste  heat  of 
the  fire,  and  then  runs  down  through  a  pipe  into  the  retort, 
where  it  is  converted  into  vapor.  This  vapor  enters  a  large 
brick  chamber,  and  is  there  condensed.  At  first,  when  the 
walls  are  cold,  a  fine  powder  is  produced,  known  in  com- 
merce as  flowers  of  sulphur  ;  but  afterwards,  when  the  walls 
of  the  chamber  become  hot,  the  sulphur  condenses  to  a  liquid, 


PROPERTIES  OF  SULPHUR. 


151 


which  collects  on  the  floor  and  may  be  drawn  off  and  ladled 
into  moulds,  forming  what  is  ordinarily  called  roll  brim- 
stone. 

Sulphur  is  also  obtained  from  iron  disulphide  or  pyrite, 
a  mineral  which,  in  some  localities,  is  very  abundant.  For 
this  purpose  the  pyrite  is  piled  up  in  a  pyramid  with  wood, 


Fig.  27.  Refining  of  Sulphur. 

and  fire  applied.  The  sulphur  which  is  set  free  collects  in 
the  liquid  form  in  cavities  made  in  different  parts  -of  the 
heap.  The  pyrite  gives  up  one  third  of  its  sulphur  when 
thus  treated,  yielding  about  20  per  cent  of  its  weight. 

197.  Properties. — I.  PHYSICAL. — Sulphur  is  capable  of 
existing  in  three  distinct  allotropic  forms  or  modifications, 
due  without  doubt  to  varying  molecular  atomicity : 

(V)  The  first  variety  is  that  found  in  nature.  It  is  a 
lemon-yellow,  brittle  solid,  crystallizing  in  ortho-rhombic  octa- 
hedrons, often  modified  (Fig.  28,  1,  and  2),  and  possessing  a 


152  IXORGAXTC  CHEMISTRY. 

specific  gravity  of  2'05.  It  is  easily  soluble  in  carbon  disul- 
phide  and  may  be  readily  crystallized  therefrom., 

(/?)  The  second  variety  is  produced  by  crystallizing  sul- 
phur from  fusion,  at  high  temperatures.  Yellowish-brown 
needle-shaped  crystals  belonging  to  the  monoclinic  system 
(Fig.  28,  3),  are  thus  obtained,  which  are  transparent  and 
have  a  specific  gravity  of  1'98.  This  variety  also  is  soluble 
in  carbon  disulphide,  and  passes,  slowly  at  ordinary  temper- 
atures, more  rapidly  at  higher  ones,  back  into  variety  a. 

Sulphur,  since  it  crys- 
tallizes in  forms  belonging 
to  two  distinct  systems,  is 
called  a  dimorphous  ele- 
ment. 

(Y)    The    third  variety 
of  sulphur  is  produced  by 
heating  melted  sulphur  to 
Fig.  28.  sulphur  Crystals.  a  temperature  of  250°  and 

then  suddenly  cooling  it  by  pouring  it  into  water.  It  is  a 
dark  brown,  tenacious  mass,  which  may  be  drawn  out  in 
threads  like  caoutchouc.  It  has  a  specific  gravity  of  1  •!)•"), 
and  is  only  partially  soluble  in  carbon  disulphide,  an  amor- 
phous powder  remaining  uudissolved.  It  slowly  passes  into 
«  if  left  to  itself;  but  if  heated  to  100°,  it  undergoes  this 
change  suddenly,  the  temperature  rising  to  110°  from  the 
heat  evolved. 

Eitlfer  variety  of  sulphur  melts  when  heated  to  111°,  be- 
coming a  pale -yellow  limpid  liquid.  As  the  temperature 
rises  it  becomes*  viscid,  until  between  200°  and  250°  the 
vessel  may  be  inverted  without  loss ;  it  then  becomes  fluid 
again,  and  at  440°  boils.  Its  vapor-density  was  for  a  long 
time  considered  anomalous,  being  at  500°,  96 ;  but  Bineau 
showed  that  at  1000°  it  became  normal,  32.  The  molecule 
of  sulphur  at  500°  is  therefore  hex-atomic,  while  at  1000°  it 
is  di-atomic. 


SVL/'HL'II. 


153 


EXPERIMENTS. — To  produce  the  t1  variety  of  sulphur,  melt  250 
grams  ,of  this  substance  in  a  crucible  over  a  gas-flame  or  in  a  char- 
coal fire.  Allow  it  to  cool 
until  a  crust  forms  upon  the 
surface.  Pierce  a  hole  in  this 
crust  near  one  side,  and  pour 
out  the  sulphur  which  still 
remains  liquid.  The  interior 
of  the  crucible  when  cold  will 
be  found  lined  with  needle- 
shaped  crystals.  (Fig.  29.) 

The    third    or   amorphous 

variety  of  sulphur  may  be  prepared  by  melt- 
ing a  sufficient  quantity  in  a  flask,  heating  it 
until  the  second  stage  of  fluidity  is  readied, 
and  then  pouring  it,  in  a  thin  stream,  into 
water,  as  shown  in  Fig.  30.  On  removing  it 
from  the  water,  it  is  found  to  be  remarkably 
plastic;  thus  affording  an  excellent  example  of  allotropism. 


Fig.  29.  Mono- 
clinic  Sulphur 
Crystals. 


Fig.  oO.   Preparation  of 
Amorphous  Sulphur. 


II.  CHEMICAL.— When  heated  to  260°  in  the  air,  sulphur 
takes  fire,  burning  with  a  pale  blue  flame.  It  is  also  a  sup- 
porter of  combustion,  many  metals  taking  fire  readily  in  its 
vapor  and  burning  actively.  When  united  with  other  ele- 
ments it  forms  sulphides. 

Berthelot  proposes  to  call  the  insoluble  variety  of  sulphur 
electro -positive,  and  the  soluble,  electro  -  negative,  because 
these  forms  of  sulphur  are  due,  in  his  opinion,  to  the  element 
with  which  the  sulphur  has  previously  been  united.  When 
separated  from  union  with  the  more  negative  oxygen,  for 
example,  the  sulphur  is  found  insoluble  and  electro-positive ; 
while,  obtained  from  its  hydrogen  compound,  it  is  soluble 
and  electro-negative. 

When  combined  with  positive  elements  alone,  sulphur 
acts  as  a  dyad  and  is  then  the  analogue  of  oxygen.  As  a 
dyad  too,  it  may  perform  a  linking  function. 

198.  Tests. — In  the  free  state  sulphur  is  recognized  by 
its  color,  by  its  volatility  when  heated,  and  by  its  odor  when 


154 

burned.      In  combination,  as  a  soluble  sulphide,  it  blackens 
paper  moistened  with  a  solution  of  lead  acetate. 

199.  Uses. — Sulphur  is  employed  very  largely  in  the  arts 
in  the  manufacture  of  gunpowder,  in  the  preparation  of  sul- 
phuric acid,  in  the  vulcanization  of  india-rubber,  and  for 
bleaching  straws  and  woolens. 

SULPHUR   AND    HYDROGEN. 

HYDROGEN  SULPHIDE. — Formula  H,S.  Molecular  /////.s.s  33*98. 
Molecular  volume  2.  Relative  density  16*99.  The  HKIM  <>f  1 
liter  is  1*52  gram*  (17  critlt*). 

200.  History  and  Occurrence. — Hydrogen  sulphide — 
called  also  hydrosulphuric  acid  and  sometimes  sulphuretted 
hydrogen — was  discovered  by  Scheele  in  1777.     It  occurs  in 
certain  volcanic  gases,  and  is  the  essential  constituent  of  the 
water  of  the  so-called  sulphur  springs,  such  as  Sharon  and 
Avon  in  this  country,  Harrowgate  in  England,  Bagnieres  in 
France,  and  Aachen  in  Germany. 

201.  Preparation  and   Properties. — Hydrogen   sul- 
phide may  be  prepared  by  the  direct  union  of  its  compo- 
nents, as  by  passing  sulphur  vapor  and  hydrogen  through 
a  red-hot  tube,  filled  with  fragments  of  pumice  to  increase 
the  heated  surface.     It  is  generally  obtained  by  the  action 
of  an  acid  upon  some  sulphide.     When  ferrous  sulphide,  for 
example,  is  treated  with  sulphuric  acid  at  the  ordinary  tem- 
perature, the  reaction  is : 

FeS      +  '    H,(SO4)    =    Fe(SO4)      -f      H2S 

Ferrous  sulphide.     Hydrogen  sulphate.     Ferrous  sulphate.    Hydrogen  sulplii<l<'. 

Or,  when  antimonous  sulphide  is  heated  with  hydrochloric 
acid,  antimonous  chloride  and  hydrogen  sulphide  result: 

Sb&    +     (HC1)6    =     (SbCl3), 


EXPERIMKNTS. — For  the  continuous  preparation  of  hydrogen  sul- 
phide from  ferrous  sulphide  arid  dilute  sulphuric  acid,  Kipp's  appa- 
ratus, shown  in  Fig.  31,  is  convenient.  It  consists  of  three  bulbs  of 


PROPERTIES  or  HYDROGEN  SULPHIDE.  lOO 

glass,  the  two  lower  ones  being  in  a  single  piece,  and  the  upper  one, 
prolonged  by  a  tube  re^hing  to  the  bottom  of  the  lower,  being 
ground  air-tight  into  the  neck  of  the  second. 
Through  the  tubulure  of  the  middle  bulb,  the 
ferrous  sulphide,  in  lumps  the  size  of  a  chest- 
nut, is  introduced,  the  space  between  the  tube 
and  the  side  of  the  constriction  being  too 
narrow  to  let  them  fall  through.  This  tubu-  * 
lure  is  then  closed  by  a  cork  through  which 
a  glass  stop  cock  passes.  The  acid — one  part 
sulphuric  acid  diluted  with  fourteen  of  water 
— is  poured  in  through  the  safety  tube,  runs 
into  the  bottom  globe,  and  rises  to  overflow 
the  iron  sulphide  in  the  middle  one.  If  the 
cock  is  open,  the  gas  which  is  evolved  escapes; 
but  when  it  is  shut,  the  pressure  of  the  accu- 
mulating gas  forces  the  liquid  away  from 
the  sulphide  down  into  the  lower,  and  thence 
into  the  upper  bulb,  thus  stopping  the  action 
and  preserving  a  volume  of  the  gas  ready 
for  use.  By  the  tubulure  of  the  lower  bulb  Fig.  31.  Hydrogen  Sulphide 
the  acid,  when  saturated,  may  be  removed.  Apparatus. 

Hydrogen  sulphide  is  a  colorless  gas,  with  a  disgusting 
odor,  well  known  as  that  of  rotten  eggs.  It  is  somewhat 
heavier  than  air,  its  specific  gravity  being  1*177.  Cooled  to 
—  74°,  or  submitted  to  a  pressure  of  17  atmospheres  at  10°, 
it  condenses  to  a  colorless  mobile  liquid  of  specific  gravity 
0'9,  which  freezes  to  a  mass  like  ice  at  — 85°.  It  is  quite 
soluble  in  water,  1  volume  of  which  dissolves  3  volumes  at 
ordinary  temperatures,  and  4%37  volumes  at  0°.  Chemically, 
hydrosulphuric  acid  gas  is  combustible,  burning  with  a  pale 
blue  flame.  Its  reaction  with  blue  litmus  paper  is  weakly 
acid.  It  is  easily  decomposed  by  a  temperature  of  400°  and 
by  oxidizing  agents,  the  sulphur  frequently  being  deposited. 
It  reacts  with  metals  and  their  oxides  to  produce  sulphides, 
setting  hydrogen  free  in  the  first  case,  and  water  in  the  sec- 
ond. This  gas  is  exceedingly  poisonous ;  according  to  Fara- 


156  i xona  AXIC  (  'HEM fs rn } '. 

day,  birds  die  in  air  which  contains  but  ysVo  °^  ^>  and  dogs 
in  that  which  contains  but  -g^j--^. 

Hydrogen  sulphide  is  feebly  exothermic,  the  reaction  being, 
when  the  sulphur  is  solid  and  the  hydrogen  and  hydrogen 
sulphide  gaseous  : 

(H2),  +  S2  =  (H2S)2  +  9,000  water-gram  degrees. 

Inasmuch  as  the  solution  of  hydrogen  sulphide  in  water 
evolves  9,400  units  of  heat,  it  follows  that  the  formation  of 
a  solution  of  this  gas  from  its  elements  evolves  18,400  heat- 
units.  It  is  evidently  this  low  heat  of  formation  which  ren- 
ders its  direct  synthesis  so  difficult,  and  which  renders  the 
gas  so  easily  decomposed  by  heat. 

2O2.  Tests  and  Uses. — Hydrogen  sulphide  is  easily  de- 
tected by  placing  in  it  a  strip  of  paper  moistened  with  a 
solution  of  lead  acetate ;  in  this  way  it  may  be  shown  to 
exist  in  most  specimens  of  coal-gas,  and  in  the  gaseous  exha- 
lations from  drains,  cess-pools,  and  the  like.  AVith  sodium 
nitroferrocyanide  in  alkaline  solution,  it  strikes  a  deep  purple 
color. 

It  is  used  extensively  in  the  laboratory  as  a  re-agent,  the 
sulphides  which  it  produces  being  characteristic  for  certain 
metals,  either  in  color,  solubility,  or  in  some  other  easily  rec- 
ognized property. 

•  EXPERIMENT.  —  The  action  of  hydrogen  sulphide  upon  metallic 
solutions  may  be  very  well  shown  by  the  apparatus  represented  in 
Fig.  32.  The  gas  is  evolved  from  ferrous  sulphide  in  the  two-necked 
bottle,  and  passes  successively  through  the  four  solutions  in  the  ad- 
joining bottles,  the  escaping  gas  being  retained  in  a  solution  of  am- 
monia. In  the  first  bottle  may  be  placed  a  dilute  acid  solution  of 
lead,  in  the  second  one  of  arsenic,  in  the  third  one  of  antimony,  and 
in  the  fourth  one  of  zinc,  the  last  being  made  slightly  alkaline  with 
ammonia.  The  sulphide  of  lead  in  the  first  bottle  will  be  black,  the 
sulphide  of  arsenic  in  tbe  second,  yellow,  tbe  sulphide  of  antimony  in 
the  third,  orange,  and  the  sulphide  of  zinc  in  the  fourth,  white.  The 
first  three  metals  are  precipitated  in  acid  solutions,  the  last  only  when 
the  solution  is  alkaline. 


157 


The  gas  may  readily  be  inflamed  by  applying  to  it  a  lighted  tape:. 
By  holding  a  bell-glass  over  an  ignited  jet  of  this  gas,  it  is  bedewed 
with  moisture,  thus  proving  that  the  gas  contains  hydrogen.  More- 
over, on  filling  a  tube,  the  closed  end  of  which  is  bent  so  that  it  can 


n 


.  ;5-.    Precipitation  of  Metals  by  Hydrogen  Sulphide. 

be  placed  horizontally,  with  hydrogen  sulphide  over  mercury,  placing 
a  fragment  of  metallic  tin  in  the  horizontal  portion  and  heating  it, 
the  gas  will  be  decomposed,  the  tin  forming  a  sulphide  with  the  sul- 
phur and  setting  the  hydrogen  free.  As  the  volume  of  the  gas  re- 
mains unchanged,  it  is  evident  that  hydrogen  sulphide  contains  its 
own  volume  of  hydrogen. 

OXIDES    AND    ACIDS    OF    SULPHUR. 

203.  Sulphur  may  unite  with  oxygen  as  a  dyad,  tetrad, 
or  hexad,  and  may  therefore  form  the  following  series  of 
oxides  and  dibasic  acids : 

Hyposulphurous  oxide  S"O  Hyposulphurous  acid  H2S"O., 

Sulphurous  oxide  Siv().2  Sulphurous  acid  H2S"VO3 

Sulphuric  oxide  SVI0,  Sulphuric  acid  H,SV'O4 

Hyposulphurous  oxide  is  unknown. 

204.  Hypos  ulplmrous  Acid.  —  Formula  H2SO2.     Mo- 
lecular mass  65*90.     Molecular  volume  2  (?).     This  acid  was 
obtained  by  Sehutzenberger  by  the  reduction  of  sulphurous 
acid  by  means  of  zinc  : 

Zn  +  (H2S03)2  =  ZnS03  +  H,SO,  -f  H.2O 
A  yellow  solution  resulted  which  decolorized  litmus  and  in- 
digo solutions  readily.    The  acid  combines  readily  with  oxv- 


158 

gen,  and  is  a  more  active  reducing  agent  than  sulphurous 
acid.  It  is  decomposed  on  standing  in  the  air,  producing  at 
first  thio-sulphuric  acid  and  then  sulphurous  acid,  water  and 
sulphur. 

SULPHUROUS  OXIDE.  —  Formula  SO.,.  Molecular  maxs  63*9. 
Molecular  volume  2.  Eelatur  d(<n*!ti/  31-95.  The  max*  of  1 
liter  is  2  '86  grams  (32  crithz). 

205.  History  and  Occurrence.  —  Sulphurous  oxide  was 
first  pointed  out  as  a  peculiar  substance  by  the  alchemist 
Stahl  ;  but  not  until  1774  did  Priestley  carefully  examine 
its  properties.     It  is  found  among  the  gaseous  products  of 
volcanic  action. 

206.  Preparation.  —  Sulphurous  oxide  is  uniformly  the 
product  of  the  combustion  of  sulphur  in  air  or  in  pure  oxy- 
gen ;  being  formed  thus  : 

S,    +    (O,)2    =    (SO,), 

It  is  also  the  product  of  the  action  of  certain  metals,  such 
as  copper  and  mercury,  upon  sulphuric  acid.  The  metal 
simply  displaces  the  radical  of  the  acid  : 

Cu    +    ^)}0,   =    C£>,      +       HO., 

**|       )  X12    ) 

Copper.          Sulphuric  acid.        Copper  hi/ilro.cide,.      Sufylturow  oxide. 

The  copper  hydroxide  then  reacts  with  another  molecule  of 
sulphuric  acid,  thus  : 


Copper  hydroxide.         Sulphuric  acid.  Copper  sulphate.  Wafer. 

2O7.  Properties.  —  Sulphurous  oxide  is  a  colorless  gas, 
with  a  pungent  suffocating  odor,  known  as  that  of  a  burn- 
ing sulphur  match.  It  is  more  than  twice  as  dense  as  air, 
having  a  specific  gravity  of  2  -247.  Cooled  to  —10°  by  a 
freezing  mixture,  it  condenses  to  a  thin  colorless  liquid  of 
specific  gravity  1'49,  which  becomes  solid  at  —76°.  Its 
critical  temperature  is  155  '4,  and  its  critical  pressure  is  78  '9 


S  OF  XULPHl'lfOt'S  OX  I  It  K.  159 


atmospheres.  A  temperature  of  —  60°  is  produced  by  !<>• 
evaporation.  Heated  to  1200°  under  pressure,  it  is  decom- 
posed and  yields  sulphuric  oxide  and  sulphur. 

Sulphurous  oxide  gas  is  freely  soluble  in  water,  one  vol- 
ume of  which  dissolves  at  0°,  68'86,  and  at  20°,  36*22  vol- 
umes of  this  gas,  forming  sulphurous  acid.  This  solution, 
when  cooled  to  0°,  deposits  cubical  crystals  consisting  of 
H2H03,  14  aq. 

Chemically,  sulphurous  oxide  is  neither  a  combustible  nor 
a  supporter  of  combustion;  burning  bodies  introduced  into 
it  are  at  once  extinguished.  It  unites  directly  with  chlorine 
to  form  sulphuryl  chloride,  and  with  positive  oxides  to  form 
sulphites.  Hydrogen  sulphite  or  sulphurous  acid  has 
strong  acid  properties  and  destroys  vegetable  colors,  appar- 
ently by  forming  direct  compounds  with  them.  It  exhibits 
a  decided  tendency  to  take  up  oxygen  and  to  pass  into  sul- 
phuric acid;  and  therefore  acts  as  an  energetic  reducing 
agent.  It  is  a  dibasic  acid,  and  forms  acid,  normal  and  dou- 
ble sulphites.  Its  formation  is  strongly  exothermic,  78,700 
heat-units  being  evolved  in  the  production  of  a  dilute  aque- 
ous solution  from  solid  sulphur  and  oxygen. 

EXPERIMENTS.  —  Sulphurous  oxide  is  easily  liquefied  by  passing;  it, 
previously  thoroughly  dried,  through  a  U-tube  immersed  in  ice  and 
salt,  as  shown  in  Fig.  33.  It  may  he  pre- 
served in  sealed  tubes,  or  if  the  quantity 
be  large,  in  well  -stoppered  mineral  -water 
bottles.  To  show  the  cold  produced  by  its 
evaporation,  pour  some  of  the  liquid  upon 
the  surface  of  mercury  contained  in  a  cap- 
sule, and  blow  a  current  of  air  over  it  by 
means  of  a  bellows.  The  mercury  will  be 
frozen.  Or,  pour  some  of  the  liquid  oxide 

into  a  thick  crucible  of  platinum  which  is      Fig.  33.  Condensation  of 

Sulphurous  Oxide. 
red  hot;   the  liquid  will   assume  the   sphe- 

roidal state  at  a  temperature  below  its  boiling  point.  Tf  now,  a  little 
water  be  poured  in,  the  sulphurous  oxide  will  be  instantly  vaporized 
by  the  heat  taken  from  the  water,  which  therefore  at  once  becomes 


160 


1  \OHCA  \1< '  ( 77  AM/  7.S77,'  1 '. 


ice.      Bv  some  dexterity,  the  lump  of  ice  mav  l>e  thrown   out  of  tlie 

red-hot  crucible. 

The  bleaching  power  of  sulphurous  oxide  upon  flowers  may  be 

illustrated  by  burning  some  sulphur  under  a  glass  shade  (Fig.  34), 

within  which,  on  a  tripod,  are  some 
brilliantly  colored  flowers.  The  flow- 
ers will  be  readily  bleached,  but  at  the 
same  time  will  be  very  much  wilted. 
That  the  color  is  not  destroyed  in 
these  cases,  may  be  proved  very  well 
bv  adding  some  sulphurous  acid  t.  > 
two  glasses,  each  of  which  contains 
some  fresh  infusion  of  the  purple  cab- 
bage—  an  excellent  vegetable  color 
for  testing  acidity  and  alkalinity.  The 
bleaching  action  is  but  slight  till  potas- 
sium hydroxide  solution  is  cautiously 

added,  when  the  color  entirely  disap- 
Fig.  34.  Bleaching  by  SOa.  .   J 

pears,  the  two  liquids  becoming  color- 
less. But  if  a  little  strong  sulphuric  acid  be  added  to  one,  and  a  little 
potassium  hydroxide  solution  to  the  other,  the  color  reappears  in  both  ; 
in  the -first  case  brilliant  red,  in  the  other  brilliant  green.  Ether,  ben- 
zene, arid  some  other  substances,  will  also  restore  the  color  of  bodies 
thus  bleached. 

The  deoxidizing  power  of  sulphurous  acid  may  be  shown  by  add- 
ing its  solution  to  one  of  potassium  permanganate.  The  deep  purple 
color  of  the  latter  solution  at  once  disappears. 

2O8.  Tests  and  Uses. — Sulphurous  oxide  when  free  is 
at  once  detected  by  its  pungent  odor,  and  by  its  blackening 
action  upon  paper  moistened  with  a  solution  of  raercurous 
nitrate.  In  combination  as  a  sulphite,  it  evolves  hydrogen 
sulphide  when  added  to  a  solution  evolving  hydrogen. 

In  the  arts  it  is  used  chiefly  for  bleaching  straws  and 
woolens;  but  for  the  reasons  just  given,  the  bleaching  in 
not  permanent  as  it  is  with  chlorine,  but  requires  to  be  fre- 
quently repeated.  On  account  of  its  reducing  power  sul- 
phurous acid,  in  the  form  of  sodium  sulphite,  is  sometimes 
uaed  as  a  preserving  fluid  in  canning  fruits  and  vegetables. 


SULPHURIC  OX  IDE.  161 

SULPHURIC  OXIDE. — Formula  SO3.  Molecular  mass  79*86. 
Molecular  volume  2.  Relative  density  39:93.  The  mass  of 
one  liter  of  the  vapor  is  3 '58  grams  (40  criths). 

209.  Preparation. — Sulphuric  oxide  may  be  prepared 
by  oxidizing   sulphurous   oxide.     When  this  gas  is  mixed 
with  oxygen,  both  being  perfectly  dry,  and  the  mixed  gases 
are  passed  over  heated  platinized  asbestus,  they  unite,  and 
form  sulphuric  oxide.     Commercially,  the  gases  are  obtained 
in  the  proper  proportion  by  dropping  sulphuric  acid   into 
red-hot  platinum  retorts.     The  water  formed  is  removed  by 
}>assing  the  products  through  sulphuric  acid.     The  oxide  is 
also  obtained  by  heating  di-sulphuric  acid  or  sodium  disul- 
phate : 

H2S207     =     H2(S04)     +      SOS 

Di-sulpliuric  acid.        Sulphuric  add.       Sulphuric  oxide. 

The  vapor  evolved  is  collected  in  a  cold  and  dry  receiver. 

210.  Properties. — Sulphuric  oxide  as  thus  obtained  is 
a  white,  wax-like   solid,  crystallizing   in   silky  fibers  resem- 
bling asbestus.     Its  specific  gravity  is  1'9.     It  melts  at  16°, 
and  boils  at  46°.     On  maintaining  the  temperature  of  the 
fused  oxide   below  25°,   it  gradually  changes   into  a  solid, 
polymeric  apparently  with  the  one  just  mentioned,  and  called 
t  sulphuric  oxide;  this,  at  50°,  becomes  fluid  again,  being 
transformed  into  the  a  form.    Recent  researches  make  it  prob- 
able that  both  these  modifications  contain  water.     When  ob- 
tained perfectly  anhydrous  by  repeated  distillations,  it  is  a 
readily  mobile  liquid  having  a  specific  gravity  of  1*94  at 
K)°,  and  solidifying  in  long  transparent  needles  resembling 
niter,  fusing  at  14'8°.     The  liquid  boils  at  46'2.     It  fumes 
strongly  in  the  air  and  unites  with  water  with  the  evolution 
of  great  heat,  producing  sulphuric  acid.     Since  the  union 
of  SO,  and  oxygen  to  form  liquid  SO3  evolves  32,100  heat- 
units,  the  heat  of  formation  of  liquid  SO3  from  solid  sulphur 
and  oxygen  is  103,200  heat-units. 


1 62 

HYDROGEN  SULPHATE  OR  SULPHURIC  ACID. — Formula  H,SOr 
Molecular  mass  97 '82.  Specific  gravity  of  liquid  1*854  at  0°. 
Boils  at  325°. 

211.  History  and   Occurrence.  —  Sulphuric   acid  was 
prepared  by  Basil  Valentine  in  the  15th  century  under  the 
name  "  oleum  sulphuris  per  campanum."    Dr.  Roebuck  pro- 
posed the  present  method  of  manufacture  in  1770.    The  acid 
thus  made  is  therefore  often  called  "English"  add. 

Sulphuric  acid  occurs  free  in  the  waters  of  certain  rivers 
and  mineral  springs.  Boussingault  estimates  that  the  Rio 
Vinagre  in  South  America  carries  daily  to  the  sea  more  than 
38,000  kilograms ;  and  the  water  of  the  Oak  Orchard  min- 
eral spring,  New  York,  contains  in  each  liter  over  2-J  grains. 
It  has  also  been  observed  as  a  secretion  of  certain  mollusks ; 
the  saliva  of  Dolium  galea  Lk.  containing  nearly  3^  per  cent 
of  it.  In  the  sulphates  of  iron,  calcium,  barium,  and  stron- 
tium, forming  the  minerals  melanterite,  gypsum,  barite,  and 
celestite,  sulphuric  acid  is  also  represented. 

212.  Preparation. — Sulphuric  acid  is  prepared  by  add- 
ing water  to  sulphuric  oxide,  either  at  the  instant  of  its  for- 
mation or  subsequently : 

H.20    +    S0;j    =    H,SO, 

When  sulphur  is  boiled  in  nitric  acid,  it  is  oxidized  to  sul- 
phuric oxide,  which  unites  at  once  with  the  water  present, 
forming  sulphuric  acid.  In  the  preparation  on  the  large 
scale  there  are  two  general  stages :  1st,  the  oxidation  of  the 
sulphurous  to  sulphuric  acid  by  the  oxygen  of  the  air ;  and 
2d,  the  solution  of  the  sulphuric  oxide  in  water.  The  agent 
employed  for  carrying  oxygen  from  the  air  to  the  sulphu- 
rous oxide  is  nitrogen  tri-oxide,  N.,O,.  The  entire  process 
may  be  represented  theoretically  by  the  four  following  steps, 
although  in  fact  the  reactions  are  much  more  complicated: 
1st.  The  burning  of  the  sulphur  to  get  sulphurous  oxide  ; 

S    +    O,    =    SO, 


PR  EPA  EA  TJOX  OF  ,s  /  'LI'  II  I  IUC  ACID.  163 

2d.   The  reaction  of  the  sulphurous  and  nitrogen  oxides  : 

80.    +    NA   =    SO,    +    NA 
3d.  The  union  of  the  sulphuric  oxide  with  water: 

S03    +    H,0    =    H2S04 
4th.  The  re-oxidation  of  the  NA  ^rom  tne  air  : 

(NA),  -f  O,  =  (NA), 

In  practice  the  operation  is  conducted  in  large  leaden 
chambers,  shown  in  Fig.  35  on  the  following  page.  The 
sulphur  is  burned  in  the  furnace  seen  on  the  left,  and  the 
sulphurous  oxide  produced  passes  up  through  the  large  pipes, 
through  a  smaller  and  then  a  larger  chamber,  into  a  third, 
upon  the  floor  of  which  porous,  earthen,  terrace-shaped  ves- 
sels are  placed,  over  which  a  stream  of  nitric  acid  flows  from 
the  reservoirs  just  above.  The  reaction  wThich  takes  place 
here  is  as  follows  : 

(SO  A,  +  (HN08)2  +  H,0  =  (H2S04)2  -f  NA  • 
In  presence  of  a  limited   supply  of  steam,  the  next  reac- 
tion is  : 

(SO,),  +  NA  -f  02  +  H,0  = 


the  product  being  a  crystalline  compound  called  nitrosyl- 
sulphuric  acid.  By  the  action  of  water  this  is  decomposed 
as  follows  : 


The  third  stage  is  effected  by  blowing  steam  into  the  cham- 
bers from  a  boiler  heated  by  the  burning  sulphur,  as  shown 
in  the  figure.  The  sulphuric  acid  resulting  from  the  decom- 
position of  the  crystalline  compound  and  the  union  of  its 
sulphuric  oxide  with  water  collects  on  the  floor  of  the  cham- 
bers, while  the  N.,O2  unites  with  the  oxygen  of  the  air  pres- 
ent to  form  NA>  an(l  tnus  renews  the  oxidation.  A  cur- 
rent of  air  passes  slowly  through  these  chambers,  and  to 
prevent  loss,  especially  of  the  nitrogen  oxides,  the  escaping 


164 


INORGANIC 


PREP  AH  A  TION  OF  8  ULPH  UK  1C  A  CID.  1 65 

products  pass  up  through  a  column  of  moistened  pumice, 
seen  on  the  right,  by  which  these  are  absorbed.  The  solu- 
tion thus  obtained  is  carried  toward  the  sulphur  furnace  and 
allowed  to  trickle  slowly  over  a  series  of  inclined  shelves  in 
the  first  chamber,  where  it  meets  the  entering  sulphurous 
oxide  and  is  utilized.  A  series  of  smaller  chambers  is  gen- 
erally preferred  to  a  single  large  one.  When  the  acid  which 
accumulates  in  the  water  on  the  floor  of  the  chambers  has  a 
specific  gravity  of  1*5,  it  is  drawn  off,  concentrated  in  leaden 
vats  by  heat  until  the  specific  gravity  rises  to  1*7,  and  then 
in  a  platinum  still  or  in  retorts  of  glass,  until  most  of  the 
.water  is  driven  off  and  the  specific  gravity  rises  to  1  *83.  It  is 
then  placed  in  carboys  for  use.  In  practice  the  leaden  cham- 
bers often  have  a  capacity  of  100,000  cubic  feet,  and  pro- 
duce continuously  thousands  of  tons  per  week.  Sulphur  itself 
is  generally  employed  in  this  manufacture,  though  in  some 
cases  the  sulphurous  oxide  is  obtained  by  roasting  pyrite. 

EXPERIMENTS. — To  show  the  reducing  action  of  sulphurous  oxide 
upon  nitrogen  oxides,  place  in  a  jar  filled  with  sulphurous  oxide 
(Fig.  36)  a  stick  dipped  in  strong  nitric  acid.  Red 
fumes  of  the  reduced  nitrogen  compounds  will  at 
once  fill  the  jar,  and  soon  unite  with  the  sulphu- 
ric oxide  to  form  a  crystalline  compound  which 
lines  the  walls  of  the  vessel.  On  adding  water, 
the  crystals  dissolve  with  effervescence,  the  red 
fumes  again  appear,  and  sulphuric  acid  may  be 
found  in  the  liquid  at  the  bottom  of  the  jar. 

Upon  the  lecture-table,  the  sulphuric  acid  proc- 
ess may  be  illustrated  by  the  apparatus  shown  in  Fig.  36.  Oxidation  of 
Fig.  37.  The  lead-chamber  is  represented  by  the 
large  glass  globe,  at  first  full  of  air.  The  two-necked  bottle  on  the 
right  contains  the  materials  for  generating  N.2O2;  this  gas  enters  the 
globe,  meets  with  the  air,  and  becomes  N2O3.  By  means  of  a  mixture 
of  sulphur  and  manganese  di-oxide  contained  in  the  flask  shown  on 
the  left,  sulphurous  oxide  is  evolved  and  is  led  into  the  globe  by  the 
connecting  tube.  There  meeting  with  the  N2O3,  the  second  reaction 

given  above  takes  place,  N.,O3  and  SO2  producing  8Oj/<  QJJ**  which 


166 


INORGANIC  CHEMISTR  Y. 


lines  the  walls  of  the  globe,  now  colorless,  with  white  radiating  crys- 
tal!;. If  finally,  a  jet  of  steam  be  blown  in  frotn  the  third  flask,  the 
crystals  disappear,  the  globe  becomes  tilled  with  red  vapors,  and  sul- 


Fig.  37.  Production  of  Sulphuric  Acid. 

phuric  acid  collects  at  the  bottom.  By  renewing  the  air  from  time  to 
time,  through  the  rubber  tube  shown  on  the  right,  the  process  may  be 
made  continuous. 

213.  Properties. — Sulphuric  acid  is  a  dense,  colorless, 
oily,  and  very  corrosive  acid  liquid,  having  a  specific  grav- 
ity of  1-854  at  0°.  It  boils  about  338°  and  solidifies  when 
cooled  to  a  low  temperature ;  the  crystals,  which  have  the 
composition  H2SO4,  melting  at  10-8°.  It  may  be  distilled, 
but  suffers  a  partial  decomposition,  so  that  the  product  con- 
tains but  98'7  per  cent  of  acid ;  this  separation  into  sulphu- 
ric oxide  and  water — or  dissociation,  as  it  is  called  —  takes 
place  completely  at  higher  temperatures,  so  that  at  416°  its 
vapor-density  is  only  one  half  of  that  required  by  theory. 
Sulphuric  acid  has  a  very  strong  attraction  for  water,  com- 
bining with  it  with  the  evolution  of  great  heat.  It  attracts 
moisture  from  the  air,  and  is  often  used  to  dry  a  gas  by  caus- 
ing it  to  bubble  through  the  acid.  It  also  removes  water 
from  organic  matters  placed  in  it,  completely  charring  them. 


PROPER  TIES  OF  S  ULPH  URK '  AC  1 1). 


167 


EXPERIMENTS. — To  show  the  heat  evolved  by  the  union  of  sul- 
phuric acid  and  water,  pour  one  part  of  water  upon  four  parts  strong 
sulphuric  acid  in  a  beaker,  and  stir  the  mixture  with  a  test-tube  con- 
taining- some  ether  or  alcohol,  colored  with  alkanet,  or  other  color- 
ing matter.  The  alcohol  or  ether  will  boil  violently;  by  holding  the 
tube  in  a  stand,  the  vapor  may  be  ignited,  producing  a  voluminous 
flame. 

To  .show  its  action  on  organic  matters,  add  to  50  cubic  centimeters 
of  sulphuric  acid  an  equal  volume  of  strong  sugar-syrup.  On  stirring 
the  two  together  the  mass  will 
become  hot  and  rise  into  a 
black  porous  coal. 

The  attraction  of  sulphuric 
acid  for  water  is  now  made 
use  of  largely  in  Paris  for  the 
production  of  ice.  Fig.  38 
shows  the  apparatus  contrived 
by  Carre  for  this  purpose.  The 
water  to  be  frozen  is  placed  in 
the  flask  on  the  left,  which  is 
connected  by  a  tube  with  a 
horizontal  reservoir  contain- 
ing sulphuric  acid;  this  reser- 
voir may  be  exhausted  by  the 

air  pump,  the  sulphuric  acid 

Fig.  38.  E.  Carre's  Ice  Apparatus, 
being  constantly  agitated  by 

means  of  a  stirrer.  The  water  is  cooled  by  its  own  evaporation  under 
the  diminished  pressure;  and  as  the  vapor  produced  is  at  once  removed 
by  the  sulphuric  acid,  it  soon  congeals.  A  pint  of  water  may  be  frozen 
in  15  seconds  with  this  apparatus. 

The  sulphuric  acid  which  has  DOW  been  considered  is  the 
di-meta  form,  according  to  the  previous  classification  of  acids, 
page  44.  By  limiting  the  temperature  during  evaporation 
to  205°,  by  cooling  a  mixture  of  acid  and  water  of  specific 
gravity  1'78,  or  by  mixing  together  100  parts  "of  the  acid 
and  18 '4  parts  of  water,  an  acid  is  obtained  having  the 
composition  H4SVIO5,  which  is  mono-meta-sulphuric  acid.  It 
has  a  specific  gravity  of  1'78,  and  at  7'5°  crystallizes  in  the 
rhombic  system.  Again,  if  a  dilute  acid  be  carefully  evapo- 


168  INORGANIC  CHEMISTRY. 

rated  at  100°,  a  third  definite  compound  of  water  and  sul- 
phuric oxide  results.  It  has  the  formula  H6SVIO6,  and  is 
ortho-sulphuric  acid. 

The  common  form  of  sulphuric  acid  is  di-basic  ;  sulphates 
may  therefore  be  acid,  normal,  or  double.  Letting  M  stand 
for  a  monad  metal,  they  may  be  represented  thus  : 


Acid.  Acid  salt.  Normal  salt.          DoubU  ?nlt. 

The  other  forms  of  sulphuric  acid  given  above  have  also 
their  corresponding  salts.  A  zinc  niono-meta-sulphate  Zn"., 
SO5,  and  a  mercuric  ortho-sulphate  Hg"3SOc,  are  well  known 
compounds. 

The  solution  of  sulphuric  oxide  in  -water  evolves  36,100 
heat-units.  So  that  the  heat  of  formation  of  normal  or  ortho- 
sulphuric  acid  is  210,700  heat-units,  and  that  of  ordinary  or 
di-meta  sulphuric  acid  H2SO4  is  192,900  heat-units. 

214.  Di-sulphuric  Acid,  H,S2O7.—  Another  kind  of  sul- 
phuric acid  is  found  in  commerce,  prepared  by  the  distilla- 
tion of  partially  dried  ferrous  sulphate  in  earthen  retorts. 
It  is  a  heavy  oily  liquid  of  specific  gravity  1*9  ;  it  is  usually 
more  or  less  dark  colored,  hisses  like  a  hot  iron  when  dropped 
into  water,  and  fumes  strongly  in  the  air.  It  is  therefore 
called  fuming  sulphuric  acid,  or,  as  it  is  manufactured  largely 
in  Nordhausen  in  Saxony,  sometimes  Nordhausen  sulphuric 
acid.  The  name  di-sulphuric  acid  is  given  to  it,  because  it 
may  be  regarded  as  derived  from  two  molecules  of  sulphuric 
acid,  by  the  removal  of  one  molecule  of  water,  thus  : 

(H2SO4)2  --  H2O  =  H,SA 

When  heated,  it  decomposes  into  sulphuric  acid  and  sul- 
phuric oxide,  according  to  the  equation  : 
H2SA  =  H2S04  +  SO, 

It  is  used  for  dissolving  the  indigo  with  which  the  celebrated 
Saxony  blues  are  made. 


TESTS  FOP  SULPHURIC  ACID.  169 

Di-sulphuric  acid  is  DOW  made  commercially  by  conducting 
sulphuric  oxide,  made  by  passing  sulphurous  oxide  and  oxy- 
gen over  platinized  asbestus  at  a  high  temperature,  through 
ordinary  sulphuric  acid.  It  is  called  solid  sulphuric  acid, 
because  it  solidifies  when  cooled,  forming  crystals  which  melt 
at  35°. 

Three  sulphates  have  long  been  known  under  the  name 
of  vitriols,  because  like  glass ;  zinc  sulphate,  or  white  vitriol ; 
ferrous  sulphate,  or  green  vitriol;  and  copper  sulphate,  or 
blue  vitriol.  Because  sulphuric  acid  was  first  prepared  by 
distilling  the  second  of  these,  it  has  received  the  name  of  oil 
of  vitriol. 

215.  Tests. — The  test  for  free  sulphuric  acid  is  the  char- 
ring it  causes.     A  natural  water  containing  this  acid,  if  used 
to  moisten  paper,  will  char  it  completely  on  drying  at  100°. 
In  combination  in  a  soluble  form,  sulphuric  acid  and  sul- 
phates give  a  dense  white  precipitate  with  solution  of  barium 
chloride,  insoluble  in  acids.     If  the  sulphate  be  insoluble  in 
water,  it  may  be  recognized  by  fusing  it  with  sodium  carbon- 
ate, thus  converting  it  into  sodium  sulphate.     This  is  soluble 
in  water  and  may  be  tested  as  above.     Or,  what  is  sometimes 
preferable,  the  suspected  sulphate  may  be  heated  for  some 
time  with  pulverized  charcoal ;   it  will  thus  be  reduced  to  a 
sulphide,  which,  on  treatment  with  a  drop  of  acid,  will  evolve 
the  well-known  odor  of  hydrogen  sulphide. 

216.  Uses. —  Sulphuric  acid  is  the  most  important  sub- 
stance consumed  in  chemical  manufactures.     It  is  used  in 
the  production  of  nitric,  hydrochloric,  phosphoric,  citric,  and 
tartaric  acids ;  and  in  the  manufacture  of  soda,  of  phospho- 
rus, of  alum,  and  of  the  alkaloids.    It  is  largely  used  in  dye- 
ing, in  calico  printing,  and  in  bleaching  ;  in  the  preparation 
of  fertilizers,  and  in  the  refining  of  petroleum.     Indeed,  the 
extent  of  the  consumption  of  sulphuric  acid  by  any  nation, 
it  has  been  well  said,  is  a  true  index  of  its  commercial  pros- 
perity. 


170  INORGANIC  CHEMISTRY. 

THIONIC   ACIDS. 

Besides  the  acids  now  given,  in  which  there  is  but  one 
atom  of  sulphur  in  each  molecule,  there  are  others  contain- 
ing more  than  one  such  atom,  the  two  or  more  sulphur 
atoms  having  different  valences.  This  group  of  acids,  called 
the  thionic  series,  from  the  Greek  ftelov,  sulphur,  contains 
the  following  substances.: 

O 
II 
Thio-sulphuric  acid    H2S2O3  HS  —  S  —  OH 

O 

O      O 

II    II 

Dithionic  acid  H^S./ >f>  HO  —  S  —  S  —  OH 

O      O 
O  O 

II         II 

Trith ionic  acid  H2S3O6  HO  —  S  —  S  —  S  —  OH 

II  II 

0  O 

O  O 

II  II 

Tetra tli ionic  acid        H^Og          HO  —  S  —  S  —  S  —  S  —  OH 

II  II 

O  O 

O  O 

II  II 

Pentathionic  acid       H2S5O6      HO  —  S  —  S  —  S  —  S  —  S  —  OH 

II  il 

O  O 

217.  Thio-sulpliuric  Acid. — Hypo-sulphurous  acid 
of  some  authors.  Thio-sulphates  are  prepared  either  by  add- 
ing sulphur  to  a  sulphite  or  by  partial  oxidation  of  a  sul- 
phide. By  the  first  method  : 

Na2SO3  +  S  =  Na2S2O, 

Large  quantities  of  the  sodium  salt  were  formerly  manufact- 
ured for  use  in  photography,  under  the  name  sodium  hypo- 


RELEXITM  A XI)  TELLURIUM.  171 

sulphite.  It  is  also  used  as  an  antichlor  in  chlorine  bleach- 
ing.  The  acid  corresponding  to  it  has  not  been  prepared  in 
the  free  state,  as  it  rapidly  decomposes. 

SULPHUR   AND    CHLORINE. 

218.  The  Sulphides  of  Chlorine  are  three  in  number, 
having  the  formulas  C12S2,  C12S,  and  C14S.     They  are  formed 
by  the   direct  union   of  their  constituents,  the   first  being 
formed  when  the  sulphur  is  present  in  excess,  the  last  when 
the  chlorine  is  most  abundant.     The  chloride,  C14S,  exists 
not  only  in  the  free  state,  but  also  in  combination  with  cer- 
tain metallic  chlorides  as  SnCl4(Cl4S).2  with  stannic  chloride, 
(SbCl5)2  (C14S)3  with  antimouic  chloride,  etc. 

The  sulphurous  acid  radical  SO",  called  thionyl,  and  the 
sulphuric  acid  radical  SO/',  called  sulphuryl,  combine  with 
chlorine  to  form  thionyl  chloride  SOC12  and  sulphuryl  chlo- 

(  OH 

ride  SO2C12.  The  intermediate  compound  SO2  j  p,  ,  sulphu- 
ryl hydroxy-chloride  is  also  known. 

§  3.    SELENIUM  AND  TELLURIUM. 

SELENIUM. — Symbol  Se.  Atomic  mass  78 -87.  Molecular  mass 
157*74.  Valence  II,  IV,  VI.  Relative  density  of  vapor  78*87. 
Molecular  volume  2.  Specific  gravity  of  solid  4*5.  The  mass 
of  one  liter  of  selenium -vapor  at  1420°  is  7*08  grams  (79 
criths). 

219.  History  and  Preparation. — Selenium  was  discov- 
ered by  Berzelius  in  1817  in  the  lead-chamber  deposits  of 
the  sulphuric  acid  manufactory  at  Gripsholm.     He  named 
it  from  ffetyvy,  the  moon.     It  is  a  rare  substance,  occurring 
occasionally  free,  but  generally  combined  with  copper,  lead, 
silver  and  mercury,  as*  selenides.     It  exists  also  as  an  impu- 
rity in  certain  sulphurs.     It  is  obtained  from  the  sulphuric 
acid  residues,  or  from  the  minerals  containing  it,  by  fusing 


172  IXORGJXIC  CHEMISTKY. 

with  sodium  nitrate  and  carbonate,  extracting  the  sodium 
sclenate  with  water,  and  reducing  this  with  a  solution  of 
sulphurous  acid. 

220.  Properties. — Selenium,  like  sulphur,  is  capable  of 
existing  in  at  least  two  allotropic  states :  «  Selenium,  which 
corresponds  to  «  sulphur,  is  a  dark,  grayish-black  crystalline 
solid,  of  specific  gravity  4*8,  and  is  insoluble  in  carbon  di- 
sulphide.     It  is  a  conductor  of  electricity  and  has  a  metallic 
luster.     /?  Selenium,  is  dark  reddish-brown  in  color,  has  a 
specific  gravity  of  4*5,  and  is  soluble  in  carbon  di-sulphide, 
from  which  it  crystallizes  in  monoclinic  prisms.     This  is  the 
more  stable  form  of  selenium,  the  form  it  has  when  native. 
A  third  or  amorphous  variety  is  known,  having  a  specific 
gravity  4'26,  and  existing  in  two  forms,  the  one  electro-posi- 
tive and  insoluble  in  carbon  di-sulphide,  the  other  electro- 
negative and  soluble  in  this  liquid.     It  fuses  a  little  above 
100°,  and  if  suddenly  cooled  becomes  vitreous  selenium.    On 
heating  it  to  217°  and  then  suddenly  cooling  to  180°-19()°, 
keeping  this  temperature  constant  for  some  time,  the  amor- 
phous is  converted  into  the  crystalline  variety,  «  selenium. 
On  raising  the  temperature  to  150°,  /9  passes  into  a  selenium, 
with  a  distinct  evolution  of  heat,    ft  Selenium  melts  at  217°. 
The  liquid  boils  at  about  700°.     In  its  chemical  properties, 
selenium   very  closely   resembles    sulphur,   forming   similar 
compounds  with  other  elements.     It  burns  with  a  blue  flame 
and  gives  off  an  intolerable  odor  like  that  of  decaying  horse- 
radish.    It  unites  directly  with  the  metals,  forming  selenides. 

TELLURIUM. — Symbol  Te.  Atomic  mass  125*0.  Valence  II, 
IV,  and  VI.  Relative  density  of  vapor  125*0.  Molecular 
volume  2.  Specific  gravity  of  solid  6*25.  The  mass  of  1  liter 
of  tellurium-vapor  at  1390°  is  11*47  grams  (125*0  criths). 

221.  History  and  Preparation.  —  Tellurium  was  dis- 
covered by  Klaproth  in  1798,  in  a  Transylvanian  gold  ore, 
and   named   from  tellus,  the  earth.     It  occurs  even   more 


S  OF  TELLURU  M.  173 


rarely  than  selenium,  and  is  found  native  in  Colorado  and 
in  Hungary.  It  exists  also  in  combination  with  bismuth, 
lead,  gold,  and  silver.  The  mode  of  its  preparation  is  analo- 
gous to  that  of  selenium.  It  is  obtained  in  solution  either 
as  potassium  telluride,  or  as  tellurous  acid,  and  then  precip- 
itated ;  in  the  former  case  by  a  current  of  air,  in  the  latter 
by  sulphurous  acid. 

222.  Properties.  —  Tellurium  is  a  tin-white,  brittle  solid, 
having  a  strong  metallic  luster  and  a  specific  gravity  of  6*25. 
It  crystallizes  in  rhombohedrons,  and  conducts  heat  and  elec- 
tricity readily.     It  melts  at  500°,  volatilizes  at  a  white  heat, 
and  may  be  distilled.     Its  vapor  is  greenish-yellow  like  chlo- 
rine.    When  heated  in  the  air  it  takes  fire  and  burns  with  a 
blue  flame  tinged  with  green,  evolving  white  fumes  of  tel- 
lurous oxide.     Indeed  in  all  its  physical  properties  it  is  a 
metal  ;  but  it  is  so  closely  allied  chemically  to  sulphur  and 
selenium,  that  it  is  considered  with  these  elements.     Its  bi- 
nary compounds  are  called  telluricles. 

RELATIONS   OF  THE   GROUP. 

223.  The  same  gradation  of  properties  is  seen  here  which 
was  noticed  in  the  chlorine  group.     As  the  atomic  weight 
increases,  the  chemical  activity  diminishes.    The  sum  of  the 
atomic  weights  of  sulphur  and  tellurium  (31  '98+  125),  is 
almost  exactly  double  that  of  'selenium,  78  '87.     They  all 
form   similar  compounds  with  hydrogen,  H2O,  H2S,  H28e, 
and  H2Te,  in  which  they  are  bivalent;   and  the  last  three 
form  oxides,  in  which  their  valence  is  four  and  six  ;  as  SO., 
and  SO3;  SeO2  and  SeO:j;  TeOa  and  TeO3,  to  each  of  which 
there  is  a  corresponding  acid. 


174  INOltGAXIC  CHEMISTRY. 


EXERCISES. 


1.  By  what  physical  and  chemical  methods  may  oxygen  be  ob- 
tained? 

2.  What  volume  does  a  gram  of  oxygen  occupy? 

3.  One  gram  of  mercuric  oxide  yields  what  mass  of  oxygen  ? 

4.  How  much  mercuric  oxide  is  required  to  yield  356  c.  c.  o£*  oxy- 
gen measured  at  15°  and  under  736  mm.  pressure? 

6.  What  mass  of  oxygen  measured  at  100°  is  necessary  to  fill  a 
gas-jar  which  holds  4-6  liters  of  water? 

6.  At  what  temperature  do  75)  c.  c.  of  oxygen  occupy  a  liter? 

7.  Calculate  the   percentage   of  oxygen  in  CuO,   MnO.^,   KC10.,, 
KN03. 

8.  How  much  potassium  chlorate  is  necessary  to  yield  a  cubic 
meter  of  oxygen?     A  kilogram? 

9.  If  the  chlorate  be  one  dollar  a  kilogram,  what  will  the  oxygen 
cost  per  cubic  meter  ? 

10.  A  liter  of  oxygen  is  required  of  the  relative  density  of  100  at  0°; 
how  much  KC1O.{  is  needed,  and  what  is  the  pressure  on  the  gas? 

11.  How  much  O  will  one  liter  of  chlorine  evolve  from  water? 

12.  From  what  is  the  name  oxygen  derived?     Illustrate. 

13.  By  what  processes  is  oxygen  obtained  commercially? 

14.  When  was  ozone  first  recognized?     By  whom? 

15.  How  may  ozone  be  produced?     What  is  Schonbein's  test? 

16.  In  what  do  oxygen  and  ozone  differ? 

17.  How  is  the  composition   of  water  proved  by  synthesis?     By 
analysis? 

18.  What  is  the  mass  of  a  cubic  meter  of  steam?     What  volume 
of  hydrogen  does  it  contain?    Of  oxygen? 

19.  One  gram  of  water  contains  what  volume  of  mixed  gases? 

20.  If  226  c.  c.  of  oxygen  and  500  c.  c/of  hydrogen,  both  at  110°, 
be  mixed  and  exploded,  what  will  be  the  composition  of  the  remain- 
ing gas,  and  what  its  volume  at  0°? 

21.  What  mass  of  potassium  chlorate  is  needed  to  evolve  the  amount 
of  oxygen  contained  in  one  c.  c.  of  water? 


KXERCTSKR.  17;" 

22.  What  mass  of  water  can  be  heated  from-  0°  to  1°  bv  the  combus- 
tion of  one  cubic  meter  of  mixed  oxygen  and  hydrogen? 

23.  What  volume  has  a  block  of  ice  the  mass  of  which  is  a  kilo- 
gram? 

24.  An  iceberg  floating  in  sea-water  of  specific  gravity  1-027,  ex- 
poses 30,000  cubic  meters  above  the  surface;  what  is  its  entire  vol- 
ume ? 

25.  Define  water  of  crystallization.     Efflorescence.     Deliquescence. 

26.  How  is  hydrogen  peroxide  prepared?   What  are  the  tests  for  it? 

§2. 

27.  How  does  sulphur  occur  in  nature?     How  is  it  purified? 

28.  Why  is  sulphur  dimorphous?     Pr-i.ve  its  allotropism. 

29.  What  is  the  mass  of  632  c.  c.  of  sulphur-vapor  at  500°?     At 
1000°? 

30.  One  liter  of  hydrogen  sulphide  contains  what  mass  of  sulphur? 

31.  500  c.  c.  H2S  requires  what  volume  of  oxygen  for  its  combus- 
tion ? 

32.  How  many  grams  of  FeS  and  of  H2S04  are  needed  to  yield  one 
cubic  meter  of  H2S?     To  saturate  one  liter  of  water  at  0°? 

33.  Name  the  oxides  and  the  acids  of  sulphur. 

34.  Sulphur  burned  in   a  liter  of  oxygen,  gives  what  volume  of 
SO,? 

35.  Ten  grams  of  S  gives  what  volume  of  SO2?     What  mass? 

36.  53  grams  of  copper  yield  how  many  c.  c.  of  sulphurous  oxide, 
measured  at  100°  and  under  750  mm.  pressure? 

37.  To  produce  100  grams  of  calcium  sulphite  requires  how  much 
SO,? 

38.  One  kilogram  of  SO3  requires  the  oxidation  of  what  volume  of 
SO,  ? 

39.  What  mass  of  H.2S207  will  yield  100  c.  c.  of  solid  SOH? 

40.  One  gram  of  sulphur  yields  what  mass  of  sulphuric  acid? 

41.  Oil  of  vitriol  of  sp.  gr.  1-773  contains  70  per  cent  of  sulphuric 
acid;  how  many  kilograms  of  such  acid  may  be  made  from  150  kilo- 
grams of  pyrite,  containing  42  per  cent  of  sulphur? 

^42.  What  are  the  chemical  changes  in  the  leaden  chamber? 

43.  To  neutralize  a  kilogram  of  lime  requires  what  mass  of  H,SO4? 

44.  How  is  sulphuric  acid  detected?     What  salts  does  it  form? 

45.  What  is  di-sulphuric  acid  and  how  is  it  made? 


176 


CHAPTER  FOURTH. 

NEGATIVE  TRIADS. 

§  1.    NITROGEN. 

Symbol  N.  Atomic  ma**  14-01.  Valence  1,  III,  and  V.  Rela- 
tive (leHxiti/  14.  Muh'cnlur  imi**  28'02.  Molecular  volume  2. 
T/i€  mo&s  o/*  o?ie  Mter  is  1'257  grams  (14  critks). 

224.  History. — Nitrogen  was  discovered  by  Rutherford 
in  1772.     He  showed  that  air,  after  it  had  been  breathed 
by  an  animal  and  washed  with  lime-water,  contained  a  gas 
which  would   support  neither  respiration    nor   combustion. 
Scheele  and  Lavoisier  soon   after  showed,  independently, 
that  this  substance  constituted  four  fifths  of  the  air.     La- 
voisier gave  it  the  name  azote,  from  a  and  !>/;.     Chaptal 
proposed  the  name  nitrogen,  from  vtrpov  and  ysw«w,  because 
a  necessary  constituent  of  niter. 

225.  Occurrence. — Nitrogen  exists  free  in  the  air,  mixed 
with  oxygen.     It  occurs  also  combined,  in  the  nitrates  of 
sodium,  potassium  and  calcium,  and  in  ammonia.     It  forms 
an  essential  component  of  many  vegetable  and  animal  sub- 
stances. 

22O.  Preparation. — The  easiest  method  of  preparing 
nitrogen  is  to  burn  out  of  a  given  volume  of  air  the  oxygen 
it  contains,  thus  leaving  the  nitrogen.  It  may  also  be  pro- 
cured by  purely  chemical  processes;  as  by  heating  ammo- 
niam  nitrite:  (NHj)NOj  =  (^  +  ^ 

or  by  passing   chlorine   gas  through   ammonia   solution   in 

excess : 

(H3N)8  +   (0,),  =  (NH.C1).  +  N, 


PROPERTIES  01'   A7  Y7.W,  A'.Y. 


177 


Fig.  39.  Preparation  of  Nitrogen. 
The  oxvgen  is  retained  bv  the 


EXPERIMENTS. — Nitrogen  may  be  obtained  from  air  by  burning- 
out  the  oxygen  by  phosphorus  or  copper.  A  fragment  of  phosphorus, 
carefully  dried,  is  placed  in  a  small 
capsule  floated  upon  the  surface  of 
water  by  a  piece  of  cork.  The  phos- 
phorus is  lighted  and  then  covered 
with  a  large  bell-  glass,  as  shown 
in  Fig.  39.  Dense  white  fumes  are 
formed  by  the  combustion,  which  fill 
the  jar;  the  oxygen  is  gradually  con- 
sumed, and  the  water  rises  to  take 
its  place.  In  a  short  time  these 
fumes  disappear,  and  the  nitrogen 
is  left  comparatively  pure. 

When  copper  is  used,  it  is  heated 
to  redness  in  a  glass  tube,  and  a 
slow  stream  of  air  is  passed  over  it. 
copper,  and  the  nitrogen  escapes  from  the  tube. 

For  the  chemical  preparation  of  nitrogen,  the  ammonium  nitrite — 
or  what  is  equivalent  to  it,  a  mixture  of  equal  parts  ammonium  chlo- 
ride, potassium  dichromate,  and  potassium  nitrite  in  three  parts  of 
water — is  beated  in  an  ordinary  flask,  and  the  gas  is  collected  over 
water. 

227.  Properties.  —  I.  PHYSICAL. — Nitrogen  is  a  color- 
less, odorless,  and  tasteless  gas,  somewhat  lighter  than  air, 
its  specific  gravity  being  0*971.  When  cooled  to  — 150°  in 
liquid  ethylene,  boiling  under  a  pressure  of  10  millimeters, 
nitrogen  is  readily  liquefied  by  a  pressure  of  about  30  atmos- 
pheres. The  critical  temperature  ;s  —146°  and  the  critical 
pressure  35  atmospheres  (Olszewski).  Under  these  condi- 
tions liquid  nitrogen  has  a  density  of  0*4552  ;  which  becomes 
0*83  at  —193°  and  one  atmosphere,  and  0*866  at  —202°  and 
0*105  atmosphere.  At  — 153*7°  its  coefficient  of  expansion 
is  0*0311.  Its  boiling  point  is  — 193°;  though  by  evaporat- 
ing it  in  vacuo  a  temperature  of  — 213°  has  been  reached. 
When  the  gas  is  compressed,  cooled  in  boiling  oxygen  and 
suddenly  expanded,  solid  nitrogen  falls  in  crystals  like  snow. 


178 

Water  dissolves   about  2*5  per  cent  of  it.     Its  refractive 
power  is  to  that  of  air  as  1*034  to  1. 

II.  CHEMICAL. — Chemically,  nitrogen  is  a' remarkably  inert 
substance,  entering  into  direct  combination  with  only  a  few 
elements,  such  as  carbon,  silicon,  boron,  and  titanium,  and, 
at  an  exceedingly  elevated  temperature,  with  oxygen.  It 
extinguishes  burning  bodies  introduced  into  it,  and  at  ordi- 
nary temperatures  is  not  itself  combustible.  It  is  irrespira- 
ble,  though  it  exerts  no  positively  injurious  action  upon  the 
tissues;  animals  die  in  it  as  they  would  in  water,  simply 
from  suffocation.  Though  so  indifferent  when  free,  the  com- 
pounds formed  by  nitrogen  are  among  the  most  energetic 
known.  The  corrosive  nitric  acid,  the  pungent  ammonia, 
the  explosive  nitre-glycerin ,  the  active  poisons  known  as 
prussic  acid  and  the  alkaloids,  all  contain  nitrogen.  Some 
chemists  have  long  believed  it  to  be  compound. 

THE    ATMOSPHERE. 

228.  Physical  Properties. — The  atmosphere  is  the  aerial 
envelope  which  surrounds  the  earth.  Careful  experiments 
by  Regnault  have  shown  that  one  liter  of  air  weighs  1*29318 
grams  at  0°,  and  under  760  millimeters  pressure  ;  it  is  there- 
fore 14'43  times  heavier  than  hydrogen,  and  is  the  standard 
of  specific  gravity  for  gases.  Torricelli  showed,  in  1643,  that 
the  pressure  of  the  air  upon  the  earth's  surface  would  sus- 
tain a  column  of  mercury  about  76  centimeters  in  height ; 
and  as  a  column  of  meYcury  of  this  height,  whose  area  is 
one  square  centimeter,  weighs  1033 '3  grams,  it  follows  that 
this  number  represents  the  atmospheric  pressure  upon  every 
square  centimeter  of  the  earth's  surface.  This  is  equivalent 
to  1,033x980,  6r  1,012,340  dynes;  a  little  more  than  one 
mega-dyne.  From  this  it  appears  that  the  entire  mass  of 
the  air  on  our  globe  is  about  equal  to  that  of  a  sphere  of  lead 
100  kilometers  in  diameter.  The  height  of  the  atmosphere  is 
unknown ;  it  is  generally  given  as  50  or  60  kilometers,  but 


CHEMICAL  MiOPEltTlES  OF  AIR.  179 

observations  upon  the  zodiacal  light  and  upon  meteoric  show- 
ers prove  that  it  may  be  from  320  to  340  kilometers  in  height. 
As  we  rise  from  the  earth,  the  density  of  the  air  diminishes 
rapidly,  according  to  Marriotte's  law ;  so  that  one  half  of  it 
is  within  four  and  one  half  kilometers  of  the  surface.  The 
barometer  shows  that  the  weight  of  the  air  fluctuates  within 
narrow  limits,  the  column  of  mercury  in  this  instrument 
varying  sometimes  as  much  as  60  millimeters  in  height. 

229.  Chemical  Properties. — Air  is  a  mixture  of  oxy- 
gen and  nitrogen  gases.     This  may  be  ascertained  both  by 


Fig.  40.  Lavoisier's  Experiment. 

analysis  and  by  synthesis.  The  former  method  is  the  one 
by  which  Lavoisier  first  established  the  composition  of  the 
air.  His  experiment,  now  a  classic  one  in  chemistry,  was 
thus  performed :  a  glass  balloon  with  a  long  neck,  bent  as 
shown  in  Fig.  40,  was  partially  filled  with  mercury  and  placed 
on  a  furnace.  The  neck  passed  down  under  the  surface  of 
the  mercury  in  an  adjoining  vessel,  and  then  up  into  a  bell- 
glass — also  full  of  air — whose  mouth  was  sealed  by  the  mer- 
cury. On  raising  the  temperature  of  the  mercury  to  near 
the  boiling  point,  a  red  powder  began  to  accumulate  upon 
its  surface,  the  volume  of  the  air  proportionally  diminish- 
ing ;  until,  at  the  end  of  twelve  days,  the  contraction  of  vol- 


180 

ume  ceased,  and  the  experiment  was  concluded.  The  gas 
contained  in  the  apparatus  was  proved  to  be  nitrogen ;  and 
by  collecting  the  red  powder  and  heating  it,  as  in  Fig.  17, 
the  mercury  was  reproduced  and  a  gas  evolved  which  had 
all  the  properties  of  oxygen. 

This  experiment  was  qualitative  ;  an  approximately  quan- 
titative experiment  may  be  made  by  taking  a  graduated  tube 
full  of  air,  placing  in  it  a  ball  of  phospho- 
rus cast  on  the  end  of  a  wire  (Fig.  41),  and 
immersing  its  mouth  in  mercury.  By  the 
slow  combustion  of  the  phosphorus,  the  ox- 
ygen will  be  removed,  and  the  mercury 
will  rise  to  fill  the  space  it  previously  occu- 
pied. The  nitrogen  will  be  left  in  the  tube. 
Knowing  the  original  volume  of  air,  its 
composition  may  be  easily  calculated.  A 
still  more  accurate  analysis  may  be  made 
by  means  of  the  eudiometer.  Fig.  42  rep- 
resents  a  convenient  form  for  the  lecture-room,  known  as 
Yolta's  eudiometer.  It  consists  of  a  strong  cylinder  of  glass, 
closed  above  and  below  by  stop-cocks,  the  lower  one  carrying 
a  funnel  for  convenience  of.  filling,  the  upper  one  a  cup  for 
holding  water,  into  which  may  be  screwed  the  long  gradu- 
ated tube,  shown  in  the  figure.  To  make  an  analysis  of  air, 
a  given  portion,  say  200  cubic  centimeters,  is  introduced  into 
the  eudiometer  —  previously  filled  with  water  and  standing 
on  the  water-cistern — by  means  of  the  measuring  glass  shown 
on  the  right.  Sufficient  hydrogen  to  combine  with  all  the 
oxygen,  say  100  cubic  centimeters,  is  then  added,  the  lower 
cock  is  closed,  and  an  electric  spark  passed  through  the 
mixture  from  the  small  ball  attached  to  the  upper  cap.  The 
hydrogen  and  oxygen  unite,  and,  on  opening  the  lower  cock, 
the  water  will  enter  to  take  the  place  of  the  gas  which  has 
disappeared.  The  long  graduated  tube  is  now  filled  with 
water,  inverted  in  the  top  cup  of  water,  and  screwed  to  its 


ANALYSIS  OF  AIR. 


181 


place.  The  top  cock  is  DOW  opened,  and,  by  depressing  the 
apparatus  in  the  cistern,  the  remaining  volume  of  gas  will 
pass  into  this  tube  and  may  be  measured. 
Assuming  that  it  measures  174  cubic  cen- 
timeters, then  the  volume  of  gas  which 
has  disappeared  must  be  300—174  or  126 
cubic  centimeters.  But  this  126  cubic 
centimeters  must  be  two  thirds  hydrogen 
and  one  third  oxygen,  this  being  the  ratio 
in  which  these  two  gases  combine  by  vol- 
ume. One  third  of  126  is  42 ;  hence  200 
cubic  centimeters  of  air  contain  42  cubic 
centimeters  of  oxygen,  and  100  volumes 
contain  21  volumes  of  oxygen. 

The  most  accurate  of  the  earlier  analy- 
ses of  air  were  made  by  Dumas  and  Bous- 
singault,  by  drawing  pure  dry  air  over 
red-hot  copper.  The  increase  in  the  mass 
of  the  copper  gave  the  mass  of  the  oxy- 
gen, and  the  increased  mass  of  the  ex- 
hausted globe  that  of  the  nitrogen  drawn 
into  it.  In  this  way  the  composition  of  the 
air  by  mass  was  directly,  and  by  volume 
indirectly,  determined  to  be  as  follows : 
By  tnass.  By  volume. 

Oxygen 23-0  20-8 

Nitrogen 77-0  79-2 

100-0  100-0 

The  air  of  different  localities,  though  nearly  constant  in  com- 
position, is  not  absolutely  so  ;  the  oxygen  may  diminish  from 
21  volumes  to  20-9,  and  in  rare  cases  even  to  20'3. 

That  the  air  is  merely  a  mechanical  mixture  of  its  con- 
stituents, and  not  a  chemical  compound,  is  proved  by  the 
following  considerations  :  1st,  its  components  are  not  united 
in  the  ratio  of  their  atomic  masses ;  2d,  the  properties  of  air 

13 


Fig.  42.  Volta's  Eudi- 
ometer. 


182  fXORGJXIC  CHEMISTRY. 

are  such  as  might  properly  be  expected  of  a  mixture  ;  3d, 
each  gas  dissolves  in  water  independently  of  the  other ;  aud 
4th,  no  change  of  volume  or  evolution  of  energy  appears 
when  air  is  made  artificially  by  placing  together  oxygen  and 
nitrogen. 

Moreover,  the  same  conclusions  follow  from  the  results  of 
liquefying  air.  Its  critical  temperature  is  not  constant,  but 
varies  between  — 140-8°  and  —143°  just  as  a  mixture  would 
do.  The  boiling  point  rises  gradually,  the  nitrogen  evaporat- 
ing the  more  rapidly.  By  proper  treatment  two  layers  may 
be  obtained,  each  having  its  own  meniscus. 

EXPERIMENTS. — A  mixture  of  oxygen  and  nitrogen,  in  the  pro- 
portion of  one  volume  of  the  former  gas  to  four  of  the  latter,  made  in 
a  jar  over  the  water-cistern,  acts,  in  reference  to  combustible  bodies, 
precisely  like  common  air.  The  contrast  between  air  and  its  constit- 
uents may  be  shown  by  taking  three  jars,  one  of  nitrogen,  one  of  oxy- 
gen, and  a  third  of  the  artificial  air,  made  as  above,  and  introducing 
into  them  successively  a  lighted  taper  with  a  long  wick.  In  the  first 
jar  it  will  be  extinguished,  in  the  second — provided  a  spark  is  left  on 
the  wick — it  will  be  relighted,  and  in  the  third  it  will  burn  normally, 
as  in  the  outside  air. 

Water,  on  being  boiled,  loses  the  air  which  it  has  dissolved.  On 
collecting  and  analyzing  this  air,  it  is  found  to  be  richer  in  oxygen 
than  common  air,  having  32  per  cent  of  this  gas  and  68  of  nitrogen. 
As  the  coefficient  of  solubility  of  both  these  gases  is  known,  it  is  easy 
to  calculate  what  the  composition  of  the  dissolved  gases  should  be,  on 
the  supposition  that  the  air  is  a  mixture.  Calling  the  air  one  fifth 
oxygen  and  four  fifths  nitrogen,  and  the  coefficient  of  solubility  of 
oxygen  -046  and  of  nitrogen  -025,  we  have : 

Solubility  calcitlaled.     Solubility  obserrcd. 
Oxygen         -046  X  £  =  '0092  or  31-5  32 

Nitrogen       -025  X  $  =  '0200  or  68-5  68 

•0292     100-0  100 

This  correspondence  establishes  the  fact  of  mixture,  since  every 
chemical  compound  has  a  specific  solubility  of  its  own.  This  larger 
percentage  of  oxygen  in  the  air  dissolved  by  water,  it  may  here  be 
observed,  is  essential  to  the  life  of  fishes. 


COMPOSITION  OF  AIR. 


183 


The  relative  density  of  oxygen  being  to  that  of  nitrogen 
as  16  :  14,  it  might  be  expected  that  they  would  separate, 
the  denser  oxygen  accumulating  near  the  earth.  But  we 
have  seen  that  all  molecules  are  in  constant  motion ;  and 
hence  that  all  gases  readily  permeate  or  diffuse  into  each 
other  independently  of  their  density.  The  perfection  of  this 
diffusion  is  shown  in  the  fact  that  the  variation  in  the  com- 
position of  the  air  is  as  slight  as  analysis  has  showed  it  to  be. 

EXPERIMENT. — The  relative  densities  of  oxygen  and  nitrogen,  as 
well  as  their  opposite  action  upon  flame,  may  be  well  shown  by  the 

apparatus  given  in  Fig.  43.  Two  bell- 
glasses  are  filled,  the  one  with  oxygen, 
the  other  with  nitrogen,  closed  by  plates 
of  glass  and  placed  together,  the  oxy- 
gen lowest,  as  shown  in  the  cut.  On 
removing  the  stopper  of  the  upper  jar 
and  the  plates  between  the  two,  and 
introducing  a  lighted  taper  having  a 
long  wick,  the  flame  is  extinguished  in 
the  nitrogen  but  relighted  again — if  a 
spark  be  left  on  the  wick  —  as  it  de- 
scends into  the  oxygen.  This  may  be 
repeated  several  times  before  the  gases 
become  mixed  by  diffusion. 


Fig.  43.  Properties  of  N  and  O 
contrasted. 


But  besides  these  two  chief  com- 
ponents of  the  air,  it  contains  oth- 
er substances  in  small  quantity, 
which  are  quite  as  essential.  These  are  aqueous  vapor,  car- 
bon di-oxide,  and  ammonia.  The  aqueous  vapor  varies  very 
widely  in  amount,  depending  upon  various  conditions,  espe- 
cially on  temperature.  The  quantity  of  moisture  in  the  air 
is  measured  by  the  hygrometer ;  air  is  said  to  be  saturated 
when  it  contains  all  the  moisture  it  can  hold  at  any  given 
temperature ;  thus  at  0°,  one  cubic  meter  is  saturated  by  5 -4 
grams  of  water,  at  10°  by  9 '74  grams,  and  at  25°  by  22'5 
grams.  But  the  air  in  seldom  entirely  saturated ;  60  per 


184  IXORGJXIC  CHEMISTRY. 

cent  is  regarded  as  the  healthy  mean;  but  it  may  contain 
only  one  fifteenth  of  the  saturating  quantity,  as  is  the  case 
on  the  Red  Sea  during  a  simoon.  When  the  air  is  cooled, 
the  excess  of  moisture  falls  as  rain  ;  thus  one  cubic  meter  at 
25°  cooled  to  10°  would  deposit  22*5  —  9  '74  or  12  '70  grams 
of  water.  The  carbon  di-oxide  of  the  air,  the  next  largest 
constituent,  exists  in  minute  quantity  relatively  —  about  one 
twentieth  of  one  per  cent  —  though  the  absolute  quantity  is 
large,  being  about  3,000  billion  kilograms.  It  is  estimated 
by  drawing  a  known  volume  of  air  through  a  tube  contain- 
ing potassium  hydroxide,  which  absorbs  it  and  thus  increases 
in  mass.  This  minute  amount  of  carbon  di-oxide  is  the  sole 
source  of  the  carbon  of  vegetation.  It  is  produced  by  com- 
bustion, by  the  respiration  of  animals,  by  fermentation,  and 
by  decay.  The  ammonia  present  in  air  exists  in  even  more 
minute  quantity,  being  only  from  one  to  fifty  parts  in  a  mill- 
ion of  air,  according  to  the  locality.  This  ammonia  \vashed 
down  by  the  rain  plays  an  important  part  in  yielding  nitro- 
gen to  vegetation.  Other  and  variable  constituents  there 
are  in  the  air,  such  as  gaseous  products  of  various  kinds, 
dust,  and  organic  matters.  The  latter  include  those  micro- 
scopic germs  which  produce  malaria  and  thus  may  give  rise 
to  specific  diseases.  Miller  gives  the  average  composition 
of  the  air  of  England  as  follows  : 

Oxygen    ........................  20-61 

Nitrogen  ........................  77-95 

Carbon  di-oxido  ..................  -04 

Aqueous  vapor  ..................  1-40 

Nitric  acid  ..........  ^ 

Ammonia  ..........  I  ..........  traces. 

Gaseous  hydrocarbons  J 

And  in  towns  : 

Hydrogen  sulphide  |    _ 
Sulphurous  oxide.  ,  * 


100-00 


/•A' /;/'./ //.may  OF  AM  MOM  A.  185 

NITROGEN    AND    HYDROGEN. 

HYDROGEN  NITRIDE  OR  AMMONIA. — Formula  H3N.  Molecu- 
lar mass  17*01.  Molecular  volume  2.  Relative  density  8*5. 
The  mass  of  1  liter  is  0*7635  gram  (8*5  criths). 

230.  History. — Ammonia  was  known  to  the  alchemists; 
it  was  mentioned  by  Raymond  Lully  in  the  13th  century, 
and  by  Basil  Valentine  in  the  15th.     It  was  first  obtained 
as   a   gas  by  Priestley  in    1774,   and    called    alkaline   air. 
Scheele    in   1777   showed   that  it  contained    nitrogen,   and 
Berthollet  analyzed  it  in  1785.     The  name  ammonia  was 
given  by  Bergman  in  1782,  from  that  of  its  chloride,  then 
called  sal-ammoniac ;   which  substance  was  largely  produced 
by  burning  camel's  dung  in  the  Libyan  desert,  near  a  temple 
of  Jupiter  Ammon.     It  occurs   sparingly  in  nature,  traces 
of  it  being  found  in  the  air,  in  soils,  and  in  most  mineral 
waters.     It  exists  also  in  certain  minerals  found  in  volcanic 
regions,  and  in  the  fluids  of  animals  and  plants. 

231.  Preparation.  —  Ammonia   can  not  ordinarily  be 
produced  by  the  direct  union  of  its  constituents ;  though  by 
suitable    means  they  may  be   made  to  combine  indirectly. 
When  for  example,  nitric  acid  acts  upon  zinc,  the  hydro- 
gen  which  is  set  free  in  the  atomic   form  and  hence  with 
a  stronger  than  molecular  attraction — hence  called  nascent 
hydrogen  —  unites  at  once  with  the  nitrogen,  according  to 
the  following  equation : 

(HN03)9  +  Zn4  =   (Zn(NOs)2)4  +   (H2O),  +  ~H3N 

Nitric  acid.  Zinc.  Zinc  nitrate.  Water.  Ammonia. 

Under  the  influence  of  the  silent  electric  discharge,  nitrogen 
and  hydrogen  may  combine  to  form  ammonia.  The  electric 
spark  in  moist  air  produces  ammonium  nitrate ;  and  small 
quantities  of  ammonium  nitrite  are  formed  by  the  evapora- 
tion of  water,  by  ordinary  combustion,  by  the  rusting  of  iron 
and  by  the  electrolysis  of  water.  Hence  ammonium  nitrite 
is  a  normal  constituent  of  the  atmosphere. 


The  compounds  of  ammonia  found  in  commerce  are  ob- 
tained either  by  the  destructive  distillation  of  animal  matters 
or  from  the  so-called  ammoniacal  liquors  of  the  gas-works, 
obtained  in  the  distillation  of  coal.  Ammonia  itself  is  pre- 
pared by  acting  upon  two  parts  of  ammonium  chloride — the 
sal-ammoniac  of  commerce  —  with  one  part  of  quick-lime. 
The  reaction  is  as  follows : 

(NH,HC1)2  +   CaO  =  CaCla  +   K,O  4-   (H,N)2 

The  gas  being  lighter  than  air,  may  be  collected  by  upward 
displacement. 

232.  Properties.  —  Ammonia  is  a  colorless  gas  with  a 
pungent  odor  and  a  strongly  alkaline  reaction  upon  test- 
papers.  It  is  considerably  lighter  than  air,  its  specific  grav- 
ity being  0'59.  Subjected  to  a  pressure  of  six  and  a  half 
atmospheres  at  10°,  or  to  a  cold  of  — 40°,  it  condenses  to  a 
colorless  liquid  of  specific  gravity  0*6362,  which  freezes  at 
—75°  and  boils  at  —35.7°.  The  critical  temperature  is  130° 
and  the  critical  pressure  115  atmospheres.  It  is  soluble  in 
water  to  an  extraordinary  degree ;  one  volume  of  water  at 
.0°  absorbing  1,149  volumes  of  ammonia  gas,  forming  the  so- 
called  aqua  amrnonise.  At  15°  one  volume  of  water  absorbs 
783  volumes  of  the  gas.  This  solution  has  the  well-knowrn 
properties  of  the  gas,  has  a  specific  gravity  of  0-85,  and 
evolves  the  ammonia  again  upon  heating.  For  the  prepara- 
tion of  the  ammonia  solution,  the  same  apparatus  may  be 
employed  as  was  used  for  hydrochloric  acid,  Fig.  11. 

Chemically,  ammonia  gas  has  a  strong,  but  transient  alka- 
line reaction  upon  vegetable  colors,  whence  the  name  volatile 
alkali,  sometimes  applied  to  it.  Though  containing  so  much 
hydrogen  it  is  not  combustible  in  air  at  ordinary  tempera- 
tures, though  it  burns  in  oxygen.  A  burning  candle  im<- 
mersed  in  the  gas  is  extinguished  and  animals  die  in  it  at 
once,  owing  to  the  extreme  irritation  it  causes.  Under  the 
influence  of  heat  or  of  the  electric  spark  it  is  decomposed. 


PROPERTIES  (>r  AM  MOM  A. 


187 


As  it  contains  trivulent  nitrogen  it  t-an  unite  directly  with 
other  bodies,  the  nitrogen  then  becoming  a  pentad. 

Ammonia  gas   is  an  exothermic  compound,  the  reaction 

iemg     (H2)S+N2=  (H3N)2+ 11,800  water-gram  degrees, 
all  the  substances  being  gaseous.     The  solution  of  the  gas 
in  water  evolves  8,800  heat-units ;  so  that  the  heat  of  forma- 
tion of  the  aqueous  solution  is  the  sum  of  these  values,  or 
20,600  heat-units. 

EXPERIMENTS. — The  indirect  formation  of  ammonia  may  be  very 
beautifully  shown  by  mixing  in  a  gas-holder  five  volumes  of  hydro- 
gen and  two  volumes  of  ni- 
trogen di-oxide,  and  passing 
a  stream  of  the  mixed  gases 
through  a  bulb  Lube  contain- 
ing platinized  asbestus,  as 
shown  in  Fig.  44.  So  long 
as  the  bulb  is  cold,  the  escap- 
ing gases  redden  blue  litmus 
paper;  but  on  warming  the 
bulb,  the  surface  action  of 
the  platinum  begins,  the  as- 


Fig.  44.  Synthesis  of  Ammonia. 


bestus  often  becoming  red-hot,  and  the  pungent  alka- 
line fumes  of  ammonia  appear  and  turn  the  red  paper 
back  again  to  blue. 

The  absorption  of  ammonia  gas  by  water  may  be    | 
illustrated  by  filling  a  large  bottle  with  the  gas  by 
upward  displacement,  and  closing  the  mouth  with  a 
rubber  cork  through  which  a  glass  tube  passes,  drawn 
to  a  fine  point  at  the  lower  end.     On  breaking  this 
point  beneath  the  surface  of  the  water,  as  shown  in 
Fig.  45,  the  water  will  enter  the  bottle  with  great  vio- 
lence, sometimes  crushing  it.    If  the  water  be  colored 
with  red  litmus  solution,  it  will  become  blue  as 
it  enters  the  bottle,  thus   showing  at  the  same 
time  the  alkalinity  of  the  gas. 

The  fiu:ility  with  which  ammonia  gas  may  be 
expelled  from  its  solution  by  heat,  and  the  ease 

with  which  it  may  be  condensed  to  a  liquid  by  pressure,  have  been 
made  use  of  by  F.  Carre,  of  Paris,  for  the  production  of  artificial  ice. 


FIg' 


188 


tlis  apparatus  is  represented  in  Fig.  46.  It  consists  of  a  generator 
and  receiver  made  of  iron  boiler-plate,  the  receiver  being  conical  in 

shape,  both  connected  by  means 
of  a  strong  iron  tube.  In  the 
generator  is  placed  a  strong  solu- 
tion of  ammonia  saturated  at  0°, 
and  this  is  heated  over  a  large 
gas  flame  to  130°,  the  receiver 
meanwhile  being  immersed  in 
cold  water.  The  ammonia  gas  is 
driven  off  and  is  condensed  to 
the  liquid  state  in  the  receiver, 
as  soon  as  the  pressure  passes  ten 
atmospheres.  Into  the  cylindri- 
cal space  in  the  receiver  a  closely- 
fitting  vessel  filled  with  water  is 

Fig.  46.  F.  Carre's  Ammonia  Ice-        now  placed,  and  the  apparatus  is 
machine. 

reversed,  the  generator  being  im- 
mersed in  the  water.  The  liquefied  ammonia  passes  again  into  the 
gaseous  state  and  is  re-absorbed  by  the  water  in  the  generator.  But 
in  this  evaporation  great  cold  is  pro- 
duced and  the  vessel  of  water  is  soon 
frozen.  A  larger  and  continuous  ap- 
paratus on  the  same  principle  has  also 
been  patented  by  M.  Carre. 

The  combustion  of  ammonia  in  oxy- 
gen may  be  conveniently  shown  by 
the  apparatus  represented  in  Fig.  47. 
The  gas  is  obtained  by  heating  a  strong 
solution  of  ammonia  in  the  retort,  and 
is  conducted  through  a  narrow  glass 
tube  to  a  point  just  at  the  upper  edge  rig.  47.  Combustion  of  Ammonia 
of  a  narrow  glass  cylinder,  through  in  Oxygen, 

which  passes  a  current  of  oxygen  supplied  by  the  flexible  tube.  The 
jet  of  ammonia  gas  as  it  issues,  being  surrounded  by  an  atmosphere 
of  oxygen,  takes  fire  on  the  approach  of  a  lighted  taper,  and  burns 
with  a  peculiar  yellowish  flame. 

233.  Composition. — The  composition  of  ammonia  may 
be  determined  by  introducing  a  given  volume  of  the  gas  into 
a  graduated  tube  over  mercury,  and  passing  electric  sparks 


x  or  AMMOMA.  189 


through  it.  It  is  decomposed  and  doubles  in  volume  ;  the 
pungency  and  alkalinity  of  the  gas  disappear,  and  it  is  no 
longer  soluble  in  water.  By  eudiometry,  the  volumes  of  its 
constituents  are  obtained  thus  :  assuming  that  100  cubic 
centimeters  of  ammonia  are  taken,  they  will  expand  to  200 
cubic  centimeters  on  passing  the  spark  ;  100  cubic  centime- 
ters of  oxygen  are  now  added  and  the  spark  again  passed  ; 
the  300  cubic  centimeters  become  reduced  to  75  cubic  centi- 
meters, 225  cubic  centimeters  having  disappeared.  Of  this 
225  cubic  centimeters  two  thirds,  or  150  cubic  centimeters, 
must  be  hydrogen  and  75  cubic  centimeters  oxygen.  Sub- 
tracting the  excess  of  oxygen  taken,  100—75,  or  25  cubic 
centimeters,  from  the  residual  75  cubic  centimeters  left  in 
the  eudiometer,  the  remainder,  50  cubic  centimeters,  is  nitro- 
gen. Hence  the  200  expanded  volumes  consist  of  150  vol- 
umes of  hydrogen  and  50  of  nitrogen  ;  and  ammonia  gas 
consists  of  three  volumes  of  hydrogen  and  one  volume  of 
nitrogen  condensed  into  two  volumes. 

234.  Tests.  —  Free  ammonia  is  easily  detected  by  its  odor, 
by  its  alkalinity,  and  by  the  fumes  which  it  gives  when  a  rod 
moistened  with  hydrochloric  acid  is  brought  near  it.     When 
combined,  it  may  be  set  free  by  quicklime  and  then  tested. 

DlAMINE   H4N.2  AND   HYDROXYLAMINE    (OH)H2N.  -  These 

two  compounds  are  nearly  related  to  ammonia.  The  former 
is  a  stable  gas  having  a  peculiar  pungent  odor,  and  is  very 
soluble  in  water.  It  reduces  silver  and  copper  salts  to  the 
metallic  state  and  forms  a  hydrate  H4N2  .  H.,O.  The  latter, 
produced  by  reducing  nitric  acid  with  tin,  forms  salts  analo- 
gous to  those  formed  by  ammonia,  which  salts  have  a  reduc- 
ing action  like  those  of  diamine.  Hydrazoic  acid,  HN:j,  dis- 
covered by  Curtius  in  1890,  is  a  highly  explosive  gas. 

OXIDES    AND    ACIDS    OF    NITROGEN. 

235.  —  The  oxides  formed  by  nitrogen  are  five  in  num- 
ber ;   those  normally  formed,  in  wrhich  it  has  a  valence  of 


190 

one,  three,  aiid  five ;  and  those  in  which  the  nitrogen  atom* 
are  directly  united,  and  which  may  be  viewed  as  free  radi- 
cals. Their  names,  together  with  their  corresponding  acids, 

are  as  follows : 

Oxides.  Acids. 

Hyponitrous  oxide  N'2O        Hyponitrous  acid  HN'O 

Nitrogen  di-oxide  (nitrosyl)  N'^O., 

Nitrous  oxide  N'"2O3     Nitrous  acid  HN'"<>, 

Nitrogen  tetr-oxide  (nilryl)  NV.2O4 

Nitric  oxide  NV2O5      Nitric  acid  HN^O, 

NITRIC  OXIDE. — Formula  N2O5.     Molecular  mass  107 -82. 

236.  History  and  Preparation. — Nitric  oxide,  called 
also  nitrogen  pentoxide  and  nitric  anhydride,  was  first  ob- 
tained by  Deville  in  1849.     It  is  prepared  by  the  action  of 
phosphoric  oxide  on  nitric  acid,  or  better  of  nitryl  chloride 
upon  silver  nitrate  at  60°. 

237.  Properties. — Nitric  oxide  is  a  colorless,  transpar- 
ent solid,  crystallizing  in  right  rhombic  prisms.     It  melts  at 
30°  and  boils  at  47°.     It  is  quite  unstable,  sometimes  ex- 
ploding spontaneously.     It  reacts  energetically  with  water, 
producing  nitric  acid,  thus : 

NA   +    H20   =    (HNO:t), 

HYDROGEN  NITRATE,  OR  NITRIC  ACID.  —  Formula  HNO.,. 
Molecular  mass  62*89.  Molecular  volume  2.  Relative  den- 
sity 31  '5.  TJie  mass  of  om  liter  of  nitrw-acid  vapor  is  2*82 
grams  (31*5  criths). 

238.  History.  —  Nitric  acid  was  known  to  Geber,  an 
alchemist  of  the  8th  century ;  Raymond  Lully  in  1225  de- 
scribed a  method  for  preparing  it.     Cavendish,  in  1785, 
first  determined  its  true  composition  synthetically. 

239.  Formation.  —  When    strong   electric    sparks   are 
passed  through  a  confined  portion  of  air,  standing  over  a 
solution  of  potassium  hydroxide,  the  volume  gradually  less- 
ens and  potassium  nitrate  may  be  detected  in  the  liquid.     So 


PREPARATION  or  MTRIC  ACID. 


191 


when  o/one  acts  upon  the  nitrogen  of  the  air,  upon  ammo- 
nia, or  upon  the  lower  oxides  of  nitrogen,  water  being  pres- 
ent, nitric  acid  is  produced.  Again,  when  animal  matters 
containing  nitrogen  are  allowed  to  decompose  in  presence 
of  weak  alkaline  bases,  nitrates  of  these  bases  are  produced. 
In  this  way  artificial  niter-beds  are  made. 

24O.  Preparation. — Nitric  acid  is  always  produced  by 
the  distillation  of  a  nitrate — generally  sodium  or  potassium 
nitrate — with  sulphuric  acid.  The  reaction  may  thus  be  rep- 
resented : 

Na(NO8)  +  H2(SO4)  =  HNO3  +  HNa.(SO4) 


Sodium 
nitrate. 


Sulphuric 

acid. 


Xitric 
acid. 


Hydro-sodium 
sulphate. 


EXPERIMENTS. — The  distillation  of  nitric  acid  may  be  conducted 
in  the  apparatus  given  in  Fig.  48.  The  sodium  nitrate  is  placed  in 
the  retort  on  the  right,  and  upon  it  is  poured  through  the  tuhulure, 
by  means  of  a  funnel,  an  equal  weight  of  sulphuric  acid.  The  neck 


Fig.  48.  Preparation  of  Nitric  Acid. 

of  the  retort  passes  into  that  of  the  receiver  for  a  considerable  dis- 
tance, and  the  receiver,  supported  over  a  beaker,  is  covered  with  pa- 
per to  distribute  equally  the  water  which  runs  from  the  vessel  above, 
and  which  is  intended  to  keep  it  cool.  On  lighting  the  burner,  the 
mass  liquefies,  red  fumes  appear,  and  a  more  or  less  colored  liquid 
accumulates  in  the  receiver.  By  changing  this,  collecting  the  acid 
which  comes  over  during  the  middle  of  the  operation  separately,  a 
colorless  acid  is  obtained. 


192 


In  the  arts  the  operation  is  conducted  in  a  cast-iron  retort,  as  shown 
in  Fig.  49.     A  less  concentrated  acid  is  used  for  the  decomposition, 


Fig.  49.  Commercial  Preparation  of  Nitric  Acid. 

and  two  molecules  of  sodium  nitrate  are  treated  with  one  of  sulphuric 
acid,  normal  sodium  sulphate  remaining  in  the  retort,  thus: 
(NaNO,)2  +  H,(S04)  -  Na2(8O4)  +  (HNOS)2 
The  nitric  acid  distills  over  and  is  condensed  in  the  earthen-ware 
receivers. 

241.  Properties. — Nitric  acid  is  a  colorless,  fuming,  cor- 
rosive, strongly  acid  liquid,  having  a  specific  gravity  of  1'52. 
Cooled  to  —55°  it  freezes,  and  heated  to  86°,  it  boils,  suffer- 
ing a  partial  decomposition.  It  is  also  readily  decomposed 
by  light.  Chemically,  it  is  a  powerfully  oxidizing  agent, 
acting  on  most  of  the  metals  with  great  vigor.  Nitrogenous 
animal  substances,  such  as  parchment,  silk,  and  wool,  are 
colored  strongly  yellow  by  nitric  acid.  And  many  non-nitro- 
genous vegetable  substances,  such  as  glycerin,  cotton,  and 
sugar,  are  converted  by  it  into  violently  explosive  bodies. 

The  commercial  acid  —  known  as  aqua-fortis  —  is  of  two 
sorts,  called  single  and  double.  Double  aqua-fortis  has  a 
specific  gravity  of  1*36,  and  single  of  1*22,  being  one  half 
as  strong.  A  mixture  of  nitric  acid  and  water  of  density 
1-42  has  a  definite  boiling  point,  120-5°.  But  it  is  not  a 
definite  hydrate,  the  boiling  point  being  uniform  only  under 
a  constant  barometric  pressure. 


TESTS  FOR  CITRIC  ACID.  193 

Nitric  acid  is  a  monobasic  acid,  and  can  form  only  normal 
salts,  represented  by  M(NO3),  M  being  any  monad  metal. 
But  besides  this,  which  is  the  di-meta-nitric  acid,  two  others 
are  possible,  represented  by  H;1NO4,  mono-meta-nitric  acid, 
and  H5NO5,  ortho-nitric  acid.  Lead  mouo-meta-nitrate  Pb".< 
(NO4).2,  and  bismuth  mono -meta- nitrate,  Bi'"NO4 — usually 
called  basic  nitrates  —  are  well  known  salts;  and  a  hydro- 
bismuthous  ortho-nitrate,  H2Bi'"NO5,  has  also  been  produced. 

242.  Tests. — When  free,  nitric  acid  reddens  litmus  pow- 
erfully,  bleaches  indigo  -  solution    readily,   and   evolves  red 
fumes  on  introducing  a  fragment  of  copper.    These  reactions 
are  obtained  from   nitrates  after  treatment  with  sulphuric 
acid.     Moreover,  nitrates  deflagrate  when  thrown  on  burn- 
ing charcoal. 

Nitric  acid  is  used  in  the  arts  for  etching  upon  metals, 
for  oxidizing  various  substances,  for  forming  various  substi- 
tution products,  such  as  nitro-benzol  and  picric  acid,  and  for 
the  preparation  of  nitro-glycerin,  gun-cotton,  etc. 

243.  Aqua  Regia. — Neither  nitric  nor  hydrochloric  acid 
alone  has  the  power  of  dissolving  gold,  the  rex  metallorum 
of  the  ancients.     But  a  mixture  of  one  volume   of  nitric 
and  three  of  hydrochloric   acid  contains  free  chlorine  and 
possesses  this  property,  whence  its  name  aqua  regia.     On 
submitting  this  mixture  to  a  gentle  heat,  two  exceedingly 
volatile  liquids  are  obtained  ;   one  of  these  is  nitryl  chloride 
(NO2)C1,  the  other  nitrosyl  chloride  (NO)C1.     Neither  of 
these  attack  gold. 

NITROGEN  TETR-OXIDE. — Formula  N2O4  or  -^-Q2  I  O.     Molec- 
ular mass  91 '86.     Molecular  volume  4  (Dissociation*). 

244.  Preparation. — Nitrogen  tetr-oxide  may  be  formed 
directly  by  mixing  together  two  volumes  of  nitrogen  dioxide 
with  one  volume  of  oxygen ;   although  it  is  generally  pre- 
pared by  heating  perfectly  dry  lead  nitrate: 

,),  -  (PbO)2  +  (N,0j,  +  O, 


194  lyOBdAXJC-  CHEMISTRY. 


On  passing  the  vapors  through  a  freezing  mixture,  they 
are  condensed  to  a  liquid,  or  if  perfectly  dry,  to  a  white  crys- 
talline solid  which  melts  at  —  9°.  As  the  temperature  rises, 
the  color  of  the  liquid  changes  from  yellow  to  deep  orange, 
until  it  reaches  22°,  when  it  boils,  evolving  an  orange  vapor 
which  at  40°  is  almost  black.  This  substance  furnishes  an 
interesting  example  of  dissociation  at  ordinary  temperatures. 
The  theoretical  vapor-density  for  N.2O4  is  45*9,  while  that  for 
NO2  is  22-9.  At  the  temperature  of  22°,  the  boiling  point 
of  the  liquid,  this  relative  vapor  density  is  38  ;  showing  that 
about  34  per  cent  of  the  N.,0^  is  dissociated.  At  150°  the 
vapor-density  becomes  constant  at  22*9  and  all  the  molecules 
consist  of  NO2.  This  progressive  dissociation  may  be  traced 
by  the  change  in  color  ;  N2O4  being  colorless,  while  NO2  is  a 
deep  brown,  darkening  as  above  as  the  temperature  rises. 
By  the  action  of  cold  water  it  yields  nitric  and  nitrous  acids  : 


_        2Q 
NO  p      '  H  p          H   p          H  J 

And  hence  its  constitution  must  be  ON  —  O  —  NO.,.  It  is  an 
energetic  oxidizing  agent,  many  substances  burning  in  its 
vapor.  It  combines  directly  with  chlorine  to  form  nitryl 
chloride  (NO.JC1. 

NITROUS  OXIDE  AND  ACID.  —  Formulas  N,O3  and  HNO.,. 
Molecular  mass  of  tJie  oxide  75  '90;  of  the  acid  46  '93. 

245.  Preparation.  —  Nitrous  oxide  may  be  prepared 
either  directly  by  the  union  of  four  volumes  of  nitrogen  di- 
oxide with  one  volume  of  oxygen,  or  indirectly  by  the  reduc- 
tion of  nitric  acid  by  starch  or  by  arsenous  oxide  : 

(HN08),  +  As,0;{  =  (MAs03)2  +  N.2O:( 
By  passing  the   evolved  vapors  through  a  freezing  mix- 
ture, the  nitrous  oxide  condenses  to  a  very  unstable  blue 
liquid,  which  reacts  with  water,  producing  nitrous  acid  ;  this 
is  also  a  blue  liquid,  which  may  be  preserved  at  low  temper- 


NITROUS  ACID  AND  NITRITES. 


195 


atures  unaltered,  but  is  decomposed  readily  into  nitric  acid, 
water,  and  nitrogen  di-oxide,  thus  : 

(HN02),  =  HN03  +  H20  +  N2O2 

Nitrous  acid  forms  salts  called  nitrites ;  the  mono-meta 
form  is  monobasic,  the  ortho  form,  tri basic.  Potassic  mono- 
meta-uitrite  is  KNO2 ;  this  is  the  more  common  form  of  ni- 
trite. Hydro-plumbic  ortho  -  nitrite  HPb"NO3  and  normal 
plumbic  ortho  -  nitrite  Pb"3(NO3)2  are  examples  of  actually 
known  ortho-salts. 

EXPERIMENT. — The  formation  of  nitrous  compounds  by  the  oxida- 
tion of  ammonia  may  be  illustrated  by  the  apparatus  shown  in  Fig. 
oO.  A  flask  is  one  third  filled  with  strong  ammonia  solution,  and 
placed  in  a  cup  of  sand  on  the  gas  fur- 
nace. A  spiral  of  platinum  wire  one 
third  of  a  millimeter  thick — formed  by 
winding  it  about  a  pencil — is  attached 
to  a  cork,  heated  to  redness  and  plunged 
at  once  into  the  flask.  At  the  same  time 
oxygen  gas  is  admitted  through  a  glass 
tube  which  just  dips  into  the  liquid.  The 
spiral  glows  brilliantly  in  the  gaseous 
atmosphere,  producing  at  first  white 
fumes  of  ammonium  nitrite  and  then 
red  vapors  of  nitrous  oxide.  When  the 
ammonia  gas  is  freely  evolved,  it  forms 
often  an  explosive  mixture  with  the 
oxvgen;  this,  ignited  by  the  coil,  gives 
a  slight  puff.  The  coil  cooled  by  this 
explosion  soon  again  becomes  heated,  and  the  operation  is  repeated. 
Sometimes  the  explosions  are  minute  and  take  place  rapidly  within 
the  flask,  producing  a  tone  like  that  of  the  hydrogen  tube. 

NITROGEN  DI-OXIDE. — Formula  N.,O2.  Molecular  mass  59*94. 
Molecular  volume  4  (Dissociation).  Relative  density  14*98. 
The  mass  of  one  liter  is  1*34  grams  (15  crith*). 

24C>.  History.  —  Nitrogen  di-oxide,  though  noticed  by 
Hales,  was  first  investigated  by  Priestley  in  1772. 


Fig.  50.  Combustion  of  N 
^203. 


196  IXORdAyiC  CHEMISTRY. 


247.  Preparation.  —  It  may  be  prepared  by  the  action 
of  dilute  nitric  acid  upon  metals,  such  as  copper,  silver,  or 
mercury,  or  upon  ferrous  sulphate.     With  copper,  the  reac- 
tion is  as  follows  : 

Cu,  +  (HN03)8  =  (Cu(NOO,),  +  (H,,0)4  +  N,O, 

248.  Properties.  —  Nitrogen  di-oxide  is  a  colorless  gas, 
having  a  specific  gravity  of  1*039.     Its  critical  temperature 
is  —93-5°  and  its  critical  pressure  71  '2  atmospheres.     Under 
atmospheric  pressure  it  boils  at  —  153*6°  and  solidifies  like 
snow.     There  is  an  anomaly  in  its  vapor-density,  since  its 
molecule,  if  saturated,  occupies  four  volumes  instead  of  two. 
This  is  explained  by  the  supposition  that  even  at  ordinary 
temperatures  the  molecule  is  separated  into  two  others,  each 
of  which   occupies  the  normal  volume.     This  is  known  to 
be  the  case  with  some  other  bodies,  alike  irregular  in  their 
vapor-density.     One  volume  of  this  gas  dissolves  in  about 
twenty  of  water  at  15°. 

Nitrogen  di-oxide  is  strongly  endothermic,  the  reaction 
being 

N2  +  O2  =  N.2O2  -  43,000  water-gram  degrees. 

Hence  it  may  be  exploded  by  detonating  a  little  mercuric 
fulminate  in  it  (Berthelot).  So  too,  combustion  in  this  gas 
evolves  more  heat  than  combustion  in  oxygen  ;  a  result  ex- 
plicable only  on  the  supposition  that  to  separate  N  and  O 
from  each  other  in  the  N2O2  molecule  requires  less  energy 
than  to  separate  O  and  O  from  each  other  in  a  molecule  of 
oxygen  O2. 

Nitrogen  di-oxide  extinguishes  the  flame  of  a  caudle  intro- 
duced into  it  ;  but  phosphorus  well  ignited  burns  in  it  with 
great  brilliancy,  being  able  to  take  away  its  oxygen.  It 
has  a  strong  attraction  for  oxygen,  combining  with  half  its 
volume  of  this  gas  to  form  red  fumes  of  nitrogen  tetr-oxide, 
N2O,.  It  also  unites  directly  with  chlorine,  producing  nitro- 
syl  chloride  (NOjCl. 


NITROGEN  DIOXIDE. 


197 


EXPERIMENTS. — To  prepare  nitrogen  di-oxide,  nitric  acid  of  spe- 
cific gravity  1-2 — prepared  by  diluting  the  ordinary  acid  with  twice 


Fig.  51.  Combustion  of  CS2 
and  N2O2. 


Fig.  52.  Action  of  N2O2  and  N2Os 
on  Litmus  Paper. 


its  volume  of  water — is  poured  upon  copper  clippings  contained  in  a 
two-necked  bottle  like  that  used  for  obtaining  hydrogen  (Fig.  2).  The 
gas  must  be  collected  over  water. 

A  lighted  candle  or  burning  sulphur  is 
extinguished  when  plunged  into  the  gas. 
Phosphorus  just  ignited  is  also  extin- 
guished ;  but  if  allowed  to  get  fully  on  fire 
it  burns  brilliantly.  If  a  few  drops  of  car- 
bon disulphide  be  poured  into  a  jar  of 
the  gas  and  agitated,  the  mixture  will  take 
fire  on  the  approach  of  a  flame,  as  shown 
in  Fig.  51,  burning  with  a  vivid,  intensely 
actinic  light. 

On  removing  the  cover  of  a  jar  of  nitro- 
gen di-oxide  (Fig.  52),  and  immersing  in  the 
gas  a  long  slip  of  blue  litmus  paper,  the 
lower  end  of  the  paper  in  the  pure  gas  will 
be  unaffected,  while  the  upper  end  in  con- 
tact with  the  red  fumes  produced  by  union 
with  the  oxygen  of  the  air,  will  be  turned  red.  A  somewhat  large 
bell-glass  filled  with  this  gas  gives  voluminous  clouds  of  the  brown- 
red  vapors  when  its  cover  is  removed,  as  shown  in  Fig.  53.  This 
experiment  demonstrates  the  existence  of  free  oxygen  in  the  air,  the 
N2O2  combining  with  it  to  yield  N2O3. 

14 


Fig.  53.  N202  aud  air. 


198 


INORGANIC  CHEMISTli  Y. 


HYPONITROUS  OXIDE. — Formula  N2O.  Molecular  mass  43*98. 
Molecular  volume  2.  Relative  density  21*99.  The  mass  of 
one  liter  is  1*97  grams  (22  criths). 

249.  History.  —  Hyponitrous  oxide  was  discovered  by 
Priestley  in  1776.      It  was   more   minutely  examined  by 
Davy  in  1809,  who   discovered  its   exhilarating   property. 
It  was  first  used  as  an  anaesthetic  by  Wells  in  1845. 

250.  Preparation. — Hyponitrous  oxide  maybe  prepared 
by  reducing  nitric  acid  with  zinc  or  stanuous  chloride ;  but 
it  is  generally  obtained  by  decomposing  ammonium  nitrate 
by  heat,  according  to  the  equation  : 


The  gas,  being  heavier  than  air,  may  be  collected  by  dis- 
placement. It  may  also  be  collected  over  warm  Water.  The- 
apparatus  used  is  shown  in  Fig.  54. 


Fig.  54   Preparation  of  Hyponitrous  OxicU-. 

251.  Properties. — Hyponitrous  oxide,  sometimes  called 
nitrous  oxide,  is  a  colorless  gas,  inodorous,  but  with  a  dis- 
tinctly sweet  taste.  It  is  one  half  heavier  than  air,  its  spe- 
cific gravity  being  1*527.  Cooled  to  —88°  or  subjected  to 
a  pressure  of  thirty-two  atmospheres  at  0°,  it  is  condensed 
to  a  colorless  mobile  liquid  of  specific  gravity  0*937,  which 
freezes  at  —101°.  Its  critical  temperature  is  35*4°  and  its 


FROrERTIKS  OF  HYrOMTliOUH  OXIDE.  199 

critical  pressure  is  75  atmospheres.  The  liquid  also  freezes 
by  its  own  evaporation  when  allowed  to  escape  into  the  open 
air,  producing  a  snow-like  mass,  which,  mixed  with  carbon 
disulphide  and  placed  in  a  vacuum,  produces  the  very  low 
temperature  of  — 140°.  The  gas  is  quite  soluble  in  water, 
one  hundred  volumes  dissolving  seventy-eight  volumes  at 
15°.  It  is  more  soluble  in  alcohol  and  in  alkaline  solutions. 

Burning  bodies  have  their  combustion  accelerated  in  hypo- 
nitrous  oxide.  A  candle  having  a  spark  upon  the  wick  is 
relighted  in  it,  much  as  in  oxygen.  Phosphorus  and  sulphur 
burn  in  it  with  great  splendor.  The  gas  is  decomposed,  and 
its  oxygen  unites  with  the  combustible.  When  breathed  in 
moderate  quantity  it  exerts  a  marked  exhilarative  action  on 
the  system,  and  hence  has  been  called  laughing-  gas.  Of 
late  years  it  has  come  extensively  into  use  as  an  anaesthetic 
agent,  the  inhalation  being  continued  for  a  longer  time. 
It  was  with  this  gas  that  the  property  of  anaesthesia  was  dis- 
covered; a  discovery  everywhere  acknowledged  as  one  of 
the  crowning  surgical  discoveries  of  the  present  century. 

Its  composition  may  be  ascertained  by  passing  electric 
sparks  through  it,  when  it  separates  into  two  volumes  of 
nitrogen  and  one  of  oxygen ;  or  by  exploding  it  with  an 
equal  volume  of  hydrogen,  when  its  own  volume  of  nitrogen 
only  is  left.  This  oxide,  like  all  the  oxides  of  nitrogen,  is 
an  endothermic  compound,  and  hence  can  not  be  prepared 
from  its  constituents  without  the  addition  of  energy  from 
some  external  source. 

252.  Hyponitrous  Acid. — Formula  HNO. — By  reduc- 
ing a  solution  of  "potassium  nitrate  with  sodium  amalgam, 
potassium  hyponitrite  is  obtained  ;  and  by  decomposing  silver 
hyponitrite  by  hydrogen  chloride,  the  free  hyponitrous  acid 
is  obtained.  It  is  strongly  acid,  quite  stable,  reduces  per- 
manganates, sets  free  iodine,  and  yields  hyponitrous  oxide 
on  dehydration.  The  silver  salt  decomposes  with  explosion 
above  110°. 


200  INORGANIC  CHEMIST  in. 

§  2.    PHOSPHORUS. 

Symbol  P.  Atomic  mass  30*96.  Molecular  mass  123*84.  Mo- 
lecular volume  2.  Valence  I,  III,  and  V.  Relative  detixitt/ 
61*92.  The  mass  of  one  liter  of  phosphorus-vapor  is  5*55 
grams  (62  criths). 

253.  History.  —  Phosphorus  was  discovered  in  1669,  by 
Brandt,  by  igniting  evaporated  urine  in  closed  vessels.     One 
hundred  years  later,  in  1769,  G-ahn  and  Scheele  discovered 
it  in  bones,  and  in  1775  proposed  a  method  of  preparing  it 
from  them. 

254.  Occurrence.  —  Phosphorus  does  not  occur  free  in 
nature.     It  exists  in  combination  in  the  minerals  apatite, 
pyromorphite,  wagnerite,  etc.,  which  are  calcium,  lead,  and 
magnesium  phosphates,  respectively.     Vast  deposits  of  cal- 
cium phosphate  occur  on  many  of  the  Caribbean  islands, 
and  near  Charleston,  S.  C.     The  bones  of  animals  contain 
calcium  phosphate,  and  this  as  well  as  other  phosphates  are 
present  in  their  tissues,  being  derived  mostly  from  the  seeds 
of  plants. 

255.  Preparation.  —  Phosphorus  is  prepared  by  acting 
upon  burned  bones  with  sulphuric  acid,  leaching  off  the  re- 
sulting liquid,  evaporating  it  to  dryness,  and  distilling  the 
residue  with  charcoal.     The  earthy  matter  of  bones  consists 
of  calcium  phosphate  Ca"3(PO4)2.     By  treating  this  with  sul- 
phuric acid,  acid  calcium  phosphate  results,  as  follows  : 

Ca"s(P04)2  +  (H£04),  =  (CaSO;x,  +  H4Ca"(PO4), 


Calcium  Sulphuric  Calcium        *      Hydro-calcium 

phosphate.  acid.  xulphate.  phosphate. 

This  is  leached  off  from  the  insoluble  calcium  sulphate,  and 
by  evaporation  of  the  solution  to  dryness  is  converted  into 
calcium  meta-phosphate,  thus  : 

H4Ca"(P04)2  =  Ca"(PO;j),  +   (H,O)2 
and  the  calcium  meta-phosphate  distilled  with  charcoal  gives 


PREPARATION  OF  PHOSPHORUS.  201 

phosphorus  and  calcium  phosphate  again,  according  to  the 
equation : 

(Ca"(P03)2):,  +  CIO  =  Ca"3(POJ2  +  (CO)U+P. 

Practically,  the  bones  previously  burned  and  ground  very 
fine  are  mixed  with  two  thirds  of  their  mass  of  strong  sul- 
phuric acid  diluted  with  eighteen  or  twenty  parts  of  water, 


Fig.  55.  Preparation  of  Phosphorus. 

well  stirred,  and  allowed  to  stand  for  twelve  hours.  The 
clear  liquid  is  then  strained  from  the  deposited  calcium  sul- 
phate or  gypsum,  evaporated  in  a  pan  to  a  syrupy  consist- 
ence, mixed  with  one  fifth  its  mass  of  charcoal  powder,  and 
heated  to  low  redness.  The  dry  mass  is  then  placed  in  earthen 
retorts  with  long  necks,  and  these  are  raised  gradually  to 
bright  redness  in  the  furnace  shown  in  Fig.  55,  when  the 
phosphorus  distills  over  and  condenses  in  the  receivers.  The- 
oretically, the  bone  ash  should  yield  eleven  per  cent  of  phos- 
phorus, but  practically  only  eight  per  cent  is  obtained,  unless 
enough  sand  is  added  to  form  calcium  silicate ;  then  all  the 
phosphorus  is  set  free. 

The  crude  phosphorus  is  purified  generally  by  melting  it 
under  water  and  agitating  it  with  a  mixture  of  potassium 
di-chromate  and  sulphuric  acid.  The  impurities  are  oxidized, 
and  the  pure  liquid  phosphorus  remains  colorless  and  trans- 


202 


INORGANIC  CHEMISTRY. 


parent  at  the  bottom  of  the  vessel.  It  is  then  ladled  into 
a  conical  vessel  surrounded  with  warm  water,  shown  in  Fig. 
56,  from  the  bottom  of  which  a  tube  passes,  through  a  stop- 
cock, into  another  tube  laid 
horizontally  in  a  vessel  con- 
taining cold  water,  which 
tube  can  be  closed  by  a 


plug.  On  opening  the  cock 
the  tube  fills  with  melted 
phosphorus,  which    in  the 
Fig.  56.  Casting  Phosphorus  in  Sticks.        cold    water  goon    so]idifies, 

and  may  be  withdrawn  as  a  solid  stick  by  removing   the 
plug.     In  this  form  it  is  brought  into  commerce. 

256.  Properties. — Phosphorus  is  capable  of  existing  in 
two  markedly  different  allotropic  states.  Prepared  as-above, 
«  phosphorus  is  a  colorless,  transparent,  wax-like  solid,  hav- 
ing a  specific  gravity  of  1-83.  It  melts  at  44°  to  a  colorless 
liquid  and  boils  at  290°,  yielding  a  colorless  vapor  of  specific 
gravity  4'355.  It  crystallizes  from  its  solution  in  carbon  di- 
sulphide  in  the  form  of  the  regular  dodecahedron  (Fig.  57, 1). 
It  is  not  soluble  in  water,  but 
dissolves  easily  in  carbon  disul- 
phide,  in  phosphorous  chloride, 
in  alcohol,  in  ether,  and  in  cer- 
tain volatile  and  fixed  oils.  In 
the  air  it  oxidizes  readily,  and 
hence  must  be  kept  under  wa- 
ter. Owing  to  this  slow  combus- 
tion it  is  luminous  in  the  dark,  i  rig.  57.  2 

,11  n  i  .-,  Phosphonis  Crystals. 

though  a  trace  of  naphtha  or 

oil  of  turpentine  in  the  air  prevents  this  phenomenon, 
is  violently  poisonous,  and  kills  by  depriving  the  blooc 
oxygen.  Oil  of  turpentine  is  the  best  antidote.  Heated  to 
50°  in  the  air  it  takes  fire  and  burns  vividly,  forming  phos- 
phoric oxide. 


It 
of 


HYDROGEN  PHOSPHIDE,  203 

In  1848  Schrotter  discovered  that  by  heating  ordinary 
phosphorus  to  300°  in  a  gas  which  had  no  action  upon  it,  it 
was  converted  into  a  chocolate-red  powder — /5  phosphorus — 
possessing  properties  entirely  different  from  those  previously 
exhibited.  Its  specific  gravity  is  2*14. »  At  358°  it  is  recon- 
verted into  the  «  variety.  It  is  insoluble  in  the  ordinary 
solvents  of  phosphorus,  but  it  may  be  dissolved  in  metallic 
lead  by  heating  in  a  sealed  tube  with  this  metal.  On  cool- 
ing it  crystallizes  out  in  acute  rhombohedral  crystals  (Fig. 
57,  2),  having  a  metallic  luster,  an  almost  black  color,  and 
a  specific  gravity  of  2 -34.  It  has  no.  odor,  does  not  oxidize 
readily  in  the  air,  and  is  not  poisonous.  It  does  not  take 
fire  until  heated  to  260°.  The  formation  of  the  red  phospho- 
rus from  the  white  variety  is  accompanied  by  the  evolution 
of  19,200  heat-units.  Hence  the  less  activity  of  the  former. 

257.  Uses. — Phosphorus  is  extensively  used  in  the  manu- 
facture of  friction  matches.     For  this  purpose  the  «  variety 
is  generally  employed ;   though  on  account  of  the  frightful 
disease  of  the  jaw  which  it  causes  in  the  workmen,  the  ft  or 
red  variety  is  much  to  be  preferred.     It  is  used  also  in  medi- 
cine and  as  a  rat-poison.     Its  spectrum  is  characterized  by 
two  green  lines,  readily  seen  in  the  flame  of  hydrogen  which 
has  been  passed  over  phosphorus. 

PHOSPHORUS    AND    HYDROGEN. 

Three  compounds  of  phosphorus  and  hydrogen  are  known  : 
a  gaseous  compound  H,P,  a  liquid  one  H4P2,  and  a  solid  one, 
H2P4. 

HYDROGEN  PHOSPHIDE  OR  PHOSPHINE. — Formula  H,P.  Mo- 
lecular mass  33'96.  Molecular  volume  2.  Relative  density 
16-98.  The  mass  of  one  liter  is  1'52  grams  (17  frith*). 

258.  History. — Hydrogen  phosphide  was  discovered  in 
1783  by  Gengembre;   but  its  analogy  with  ammonia  was 
first  established  by  Heinrich  Rose  in  1832. 


204 


INORGANIC  CHEMISTRY. 


259.  Preparation. — It  may  be  prepared  by  the  action 
of  water  or  of  acids  upon  phosphides : 

Ca3P,  +   (HC1)6  =   (CaCL2)3  +  (H3P)2 
by  the  decomposition  of  so-called  hypophosphorous  acid  : 
(H(P02H,))2  =  H3P04  +  HSP 

and  by  boiling  phosphorus  with  a  solution  of  potassium  hy- 
droxide : 

(HKO)3  +  P4  +  (H.O),  -  (K(P02H2))3  +  H.P 

260.  Properties. — Phosphine  is  a  colorless  gas,  with  a 
nauseous  garlic-like  odor.     It  is  sparingly  soluble  in  water, 
is  condensable  to  a  liquid,  and  is  neutral  in  its  reaction.    Its 
specific  gravity  is  1'175.     It  takes  fire  readily  at  100°,  burn- 
ing with  a  brilliant  flame.     It  unites  directly  with  hydriodic 
acid,  forming  phosphonium  iodide,  analogous  to  ammonium 
iodide  formed  from  ammonia  in  the  same  way. 

EXPERIMENT.  —  Hydrogen  phosphide  may  be  conveniently  pro- 
pared  by  the  apparatus  shown  in  Fig.  58.  The  retort  is  one  third 
filled  with  moderately  concentrated  solution  of  potassium  hydroxide, 
a  few  pieces  of  phosphorus  are  dropped  in,  and  by  means'  of  the  tube 


Fig.  r>8.  Preparation  of  Hydrogen  Phosphide. 

passing  through  the  tubulure,  the  air  is  displaced  by  a  current  of  pure 
hydrogen.  The  beak  of  the  retort  is  prolonged  by  a  glass  tube  which 
dips  beneath  the  surface  of  the  water  in  the  porcelain  dish,  thus  cut- 
ting off  contact  with  the  air.  On  heating  the  contents  of  the  retort 


OXIDES  AND  ACIDS  OF  PHOSPHORUS.  205 

to  boiling,  hydrogen  gas  first  escapes,  but  soon  bubbles  of  phosphine 
make  their  appearance,  each  one  of  which  as  it  bursts  takes  fire  spon- 
taneously—  owing  to  a  small  quantity  of  the  liquid  phosphide  dis- 
solved in  it — and  forms  a  beautiful  ring  of  white  smoke  which  rotates 
on  its  circular  axis  as  it  ascends.  If  the  air  of  the  room  be  still,  sev- 
eral of  these  rings  will  follow  each  other  to  the  ceiling.  When  the 
experiment  is  concluded,  the  hydrogen  may  be  again  passed  until  the 
gas  is  no  longer  spontaneously  inflammable. 

OXIDES    AND    ACIDS    OF  PHOSPHORUS. 

The  normal  oxides  and  acids  of  phosphorus  form  a  parallel 
series  with  those  of  nitrogen.  The  known  members  of  the 
series  are  the  following  : 

Oxides.  Acids. 

Hypophosphorous  oxide  P'.,0(?) 
Phosphorous  oxide  ~P"'.£).A 

C  Hypophosphorous  acid  H(PVQ.2H.,) 

Phosphoric  oxide  PV/),         Phosphorous  acid  H2(PVQSH) 

|    Phosphoric  acid  H3(PvQ4) 

t  Meta-phosphoric  acid     H(PVO3) 

PHOSPHORIC  OXIDE. — Formula  P2O5.     Molecular  mass  141-72. 

261.  Preparation.— Phosphoric  oxide  is  always  the  prod- 
uct of  the  rapid  combustion  of  phosphorus  in  the  air  or  in 
oxygen.  The  reaction  is  synthetic,  thus  :  Q 

P.    4-     (Q  Y    = 


EXPERIMENT. — Place  a  fragment  of  care- 
fully dried  phosphorus  in  a  small  cup  on  a 
stand,  in  the  middle  of  a  din  ing-plate;  ignite 
it  by  a  hot  wire  and  cover  it  with  a  large  bell- 
glass,  as  shown  in  Fig.  59.  White  fumes  will 
fill  the  jar,  gradually  aggregate  together  and 

fall  into  the  plate,  resembling  in  appearance 

Fig.  59.  Formation  of 
a  miniature  snow-storm.  Phosphoric  Oxide. 

262.  Properties.  —  Phosphoric  oxide  is  a  snow-white 
amorphous  powder,  which  is  fusible  at  a  red  heat  and  is 


20C)  IXORGAXIC  CHEMISTRY, 

easily  volatilized.  It  rapidly  attracts  moisture  from  the  air, 
and  adheres  together  in  flocks.  When  plunged  into  water 
it  hisses  like  a  hot  iron,  and  then  dissolves,  forming  phos- 
phoric acid.  It  is  used  for  drying  gases. 

TRI-HYDROGEN  PHOSPHATE  OR  PHOSPHORIC  ACID. — Formula 
H3PO4 .     Molecular  mats  97  '80. 

263.  Preparation. — Phosphoric  acid  is  obtained  by  the 
action  of  boiling  water  upon  phosphoric  oxide  : 

P205  +  (H,,0)3  =  (HSP04), 

by  the  oxidation  of  phosphorus  by  nitric  acid;  or  by  the 
decomposition  of  phosphates  by  sulphuric  acid  : 

Pb"8(P04),  +  (H,(S04))3  =  (Pb"(S04))8  +  (H,P04), 

Lead  phosphate.          Sulphuric  acid.  Lead  sulphate.          Phosphoric  arid. 

Commercially,  an  impure  acid  is  prepared  by  treating  bone- 
ash — calcium  phosphate — with  sulphuric  acid. 

264.  Properties.  —  As  thus  prepared,  phosphoric  acid 
is  a  syrupy  liquid,  which  by  spontaneous  evaporation  over 
sulphuric  acid  gives  hard,  transparent,  prismatic  crystals, 
which  deliquesce  in  the  air.    Their  solution  is  intensely  acid ; 
it  does  not  coagulate  albumin,  nor  precipitate  barium  chlo- 
ride.    It  throws  down  from  ammoniacal  solutions  of  magne- 
sium sulphate  a  white  crystalline   precipitate  of  ammonio- 
magnesium  phosphate,   sometimes   called   triple   phosphate. 
It  gives  with  silver  nitrate,  when  neutralized  by  ammonia, 
yellow  silver  phosphate.     On  heating  its  aqueous  solution  to 
213°,  it  gives  di-phosphoric  a.cid  ;  and  on  raising  the  temper- 
ature to  redness,  meta-phosphoric  acid  is  produced. 

This  form  of  phosphoric  acid,  being  tribasic,  is  capable  of 
forming  acid,  normal,  and  double  salts.  The  following  are 
examples  of  each: 

Acid  Salts. 

Di-hydro-sodium  phosphate  H.2NaPO4 

Hydro-di-sodium  phosphate  HNa.2PO4 

Hydro-calcium  phosphate  HCa"PO4 


META-PHOSPHORIC  ACID.  207 

Normal  Sails. 

Potassium  phosphate  K.3PO4 

Barium  phosphate  Ba//3(PO4)2 

Bismuth  phosphate  Bi"'PO4 

Double  Salts. 

Ammonio-magnesium  phosphate  (NH4)Mg"(PO4) 
Potassio-barium  phosphate  KBu"(PO4) 

The  acid  and  normal  salts  are  sometimes  called  primary, 
secondary,  or  tertiary  salts,  according  as  one,  two  or  three 
hydrogen  atoms  are  replaced  to  form  them. 

MONO-HYDROGEN  PHOSPHATE  OR  META-PHOSPHORIC  ACID. 
Formula  HPO.{.     Molecular  mass  79 '84. 

2(>5.  History  and  Preparation. — In  1833  Graham 
showed  that  ordinary  phosphoric  acid  loses  water  on  being 
heated  to  redness,  and  on  cooling  becomes  a  transparent  ice- 
like  solid,  the  so-called  glacial  phosphoric  acid : 

H,P04   -      H,0    =   HP05 

The  same  acid  is  produced  by  dissolving  phosphoric  oxide 
in  cold  water:     pA   +    H/)    =    (JJpQ^ 

Meta-phosphates  are  produced*by  igniting  acid  phosphates 
which  have  two  hydrogen  atoms : 

H2NaPO4   •      H2O   =    NaPOs 
or  which  have  two  atoms  of  volatile  base : 

H(NH4)NaP04    =    H(NH4)O    +    NaPO3 

Hydro-ammonio-Bodium        Ammonium  hydrate.       Sodium  meta- 
phosphate.  phosphate. 

By  decomposing  meta-phosphates,  the  acid  is  obtained. 

26G.  Properties. — Meta-phosphoric  acid  is  a  hard,  trans- 
parent, colorless,  glassy  mass,  not  crystallizable,  and  very 
soluble  in  water,  forming  a  strongly  acid  solution,  which 
gradually  takes  up  water  and  forms  tri-hydrogen  phosphate. 
It  coagulates  albumin  and  gives  a  white  precipitate  with 


208  INORGANIC  CHEMISTRY. 

silver  nitrate.  It  is  mono-basic,  and  forms  but  one  class  of 
salts.  It  is  distinguished  by  a  remarkable  tendency  to  pro- 
duce polymeric  forms,  called  di-,  tri-,  tetra-,  and  hexa-meta- 
phosphates,  respectively. 

The  two  phosphoric  acids  now  described  are  the  mono-  and 
di-meta  forms  of  ortho-phosphoric  acid,  H5PO5 ,  being  only 
more  distinctly  marked  examples  under  a  general  law.  Cer- 
tain ortho-phosphates,  as  the  mineral  libethenite,  hydro-di- 
cupric  ortho-phosphate  HCu",PO5,  and  di-hydro-ammouio- 
magnesium  ortho  -  phosphate  H ,  (NHj  Mg  "  PC- ,  are  well- 
known  bodies. 

DI-PHOSPHORIC  OR  PYRO-PHOSPHORIC  ACID. —  Formula 
H4P2O..     Molecular  mass  177'64. 

2O 7.  In  1826  Clark  discovered  a  variety  of  phosphoric 
acid  intermediate  between  the  two  forms  already  described, 
produced  by  heating  a  solution  of  the  tri-basic  acid  to  213°, 
and  which  for  this  reason  he  called  pyro-phosphoric  acid. 
Two  molecules  of  the  tri-hydrogen  phosphate  together  lose 
one  of  water:  (HpO<)s  _.  H/)  =  H^ 

Di-phosphates  are  produced  by  igniting  a  phosphate  which 
has  one  atom  of  volatile  base  : 

(HNa.2PO4)2     -     H2O     =     Na4P20. 

'  Hydro-di-sodium  phosphate.       Water.         &>diu>n  di-phosphate. 

It  occurs  generally  in  solution,  but  may  be  obtained  by 
evaporation  at  213°  as  a  soft  glass  or  in  semi-crystalline 
masses.  Its  solution  is  strongly  acid,  does  not  coagulate 
albumin,  and  precipitates  silver  nitrate  white.  Being  tetra- 
basic,  di-phosphoric  acid  forms  a  large  series  of  acid,  normal 
and  double  salts.  It  bears  the  same  relation  to  tribasic  phos- 
phoric acid  that  di-sulphuric  acid  bears  to  dibasic  sulphuric 
acid.  On  boiling  its  solution,  it  takes  up  a  molecule  of 
water  and  becomes  tri-hydrogen  phosphate;  on  igniting  it, 
it  loses  one,  becoming  mono-hydrogen  phosphate. 


PHOSPHOROUS  OXIDE.  209 

268.  Aldehydic  Phosphoric  Acids.— Two  other  acids 
of  pentad  phosphorus  are  known,  which,  as  they  resemble 
the  aldehydes  of  organic  chemistry,  may  be  called  aldehy- 
dic  acids.     These  are  commonly  known  as  phosphorous  and 
hypo-phosphorous  acids.     Phosphorous  acid  has  the  formula 
H.2(PO3H),  is  dibasic,  and  forms  so-called  phosphites.    Hypo- 
phosphorous  acid,  H(PO2H,),  is  mono-basic,  and  is  obtained 
by  decomposing  barium  hypo-phosphite  with  sulphuric  acid. 
Hypo-phosphites  are  formed  by  boiling  phosphorus  in  alka- 
line solutions. 

PHOSPHOROUS  OXIDE. — Formula  P2O3.    Molecular  mass  109 '8. 

269.  Preparation  and  Properties. — Phosphorous  ox- 
ide is  produced  by  the  imperfect  combustion  of  phosphorus 
in  dry  air.     For  this  purpose  the  phosphorus  is  placed  in 
a  somewhat  narrow  tube  (Fig.  60),  drawn  to  a  point  at  one 

^BB        end  and  at  the  other 

^T;   ^«aF=^^:7>-:-?^Kjtf^^»gSBi^-y  connected  with    an 

Fig.  GO.  Production  of  Phosphorous  Oxide.         aspirator,  by  means 

of  which  air  may  be 

drawn  through  the  tube.  On  heating  the  tube  the  phospho- 
rus takes  fire,  and  a  bulky  amorphous  deposit  of  phosphorous 
oxide  collects  beyond  it  in  the  tube.  The  white  flakes  are 
readily  volatile  and  have  an  alliaceous  odor.  They  are  deli- 
quescent and  dissolve  in  water  with  a  hissing  noise, 
forming  an  acid  solution.  The  rational  constitu- 
tion of  this  compound  is  unknown  ;  but  it  can 
hardly  be  normal,  since  it  does  not  give  the  nor- 
mal acid  by  the  action  of  water. 

No  acid  of  triad  phosphorus  is  certainly  known. 

270.  Hypo-phosphorous  Oxide. — By  cover- 
ing fragments  of  phosphorus  with  a  layer  of  phos- 
phorous chloride,  and  exposing  the  whole  to  the 

air,  Leverrier  obtained  a  canary-yellow   substance,  soluble 
m  water,  and  decomposing  when  boiled,  into  phosphoric  acid 


210  INORGANIC  CHEMISTRY. 

and   a   flocculent   substance    having    the    composition    P4O, 
which  could  be  heated  to  300°  without  change. 

EXPERIMENT. —  By  melting1  a  piece  of  phosphorus  under  warm 
water  (Fig.  61),  and  then  passing  into  it  a  current  of  oxygen  from  a 
gas-holder,  the  phosphorus  will  take  fire  and  burn  brilliantly  beneatu 
the  water.  The  phosphoric  acid  produced  dissolves  in  the  liquid; 
but  besides  this  a  red-brown  powder  is  formed,  which  was  formerly 
regarded  as  hypophosphorous.  oxide,  but  which  is  now  believed  to  be 
only  impure  red  phosphorus. 

§  3.    ARSENIC  AND  ANTIMONY. 

ARSENIC. — Symbol  As.    Atomic  mas*  74'9.    Valence  III  and  V. 
Relative  density  149 '8.     Molecular  mass  299'(>.     Molecular, 
volume  2.    The  mass  of  1  liter  of  arsenic  vapor  is  13*44  y  ran  us 
(150  critJis). 

271.  History. — Two  sulphides  of  arsenic  occur  native, 
one  red,  the  other  yellow.    The  former  is  mentioned  by  Aris- 
totle under  the  name  ffa^ddpd/.r^  and  the  latter  by  Dioscor- 
ides  under  the  name  apffsvtzov,  from  which  the  name  arsenic 
is  derived.     The  metal  was  first  obtained  by  Schroeder  in 
1694,  and  was  more  minutely  examined  by  Brandt  in  1733. 

272.  Occurrence. — Arsenic  occurs  somewhat  abundant- 
ly in  nature,  both  free  and  combined  with  other  metals,  as 
iron,  copper,  cobalt,  nickel,  etc.     The  most  abundant  sources 
of  it  are  the  iron  arsenides  leuco-  and  arseno-pyrite.     The 
yellow  sulphide  called  orpiment,  and  the  red  sulphide,  or 
realgar,  also  occur  native. 

273.  Preparation. — From  mispickel  or  arsenical  pyrites 
arsenic  is  obtained  by  heating  it  in  earthen  tubes  or  retorts. 
The  arsenic,  being  volatile,  sublimes  and  condenses  in  the 
cooler  portions  of  the  retort,  toward  its  mouth.     In  certain 
districts  arsenic  is  obtained  by  reducing  its  oxide  with  char- 
coal ;  this  method  gives  it  in  a  purer  form. 

274.  Properties. — Arsenic   is  a  dark,  steel-gray  brittle 
solid,  with  a  metallic  luster  and  a  specific  gravity  of  5 '6  to 


HYDROGEN  ARSENIDE.  211 

5*9.  It  occurs  in  two,  perhaps  three,  allotropic  modifica- 
tions. Besides  the  steel-gray  variety  «,  which  crystallizes  in 
rhombohedrons  and  has  the  above  specific  gravity,  there  is 
an  amorphous  black  vitreous  variety  ft,  of  specific  gravity 
4*71,  which  at  360°  passes  into  «  with  considerable  evolu- 
tion of  heat.  Arsenic  is  volatile  in  close  vessels  at  500°;  its 
vapor  is  orange  yellow,  and  has  a  peculiar  odor  resembling 
garlic.  In  the  air  it  gradually  oxidizes  at  common  tempera- 
tures, and  at  a  red  heat  it  burns  with  a  bluish-white  flame, 
producing  arsenous  oxide.  Arsenic  and  all  its  compounds 
are  active  poisons.  In  the  arts  it  is  used  in  pyrotechny,  in 
the  manufacture  of  shot,  and  as  a  fly-powder  under  the  name 
.  of  cobalt. 

ARSENIC    AND   HYDROGEN. 

HYDROGEN  ARSENIDE  OR  ARSINE. — Formula  H.,As.  Molec- 
ular mass  77 '9.  Molecular  volume  2.  The  mass  of  1  liter  is 
3-48  grams  (39  criths). 

275.  History.  —  Hydrogen  arsenide  was  discovered  by 
Scheele  in  1755. 

276.  Preparation. — It  is  always  prepared  by  the  action 
of  pure  zinc  upon  sulphuric  or  hydrochloric  acid  containing 
arsenic,  or  of  these  acids  in  the  pure  state  upon  zinc  contain- 
ing arsenic : 

As.2Zn:{     +     (HC1)(!     =     (ZnCl.2)3     -f     (H3As)2 

Zinc  arsenide.      Hydrogen  chloride.        Zinc  chloride.        Hydrogen  arsonde. 

277.  Properties. — Arsine  is  a  colorless  gas,  with  an  alli- 
aceous odor  and  a  specific  gravity  of  2-7.     Cooled  to  — 40° 
it  becomes  a  liquid,  which   solidifies  at  —119°,  and   melts 
again  at  — 113'5°.     It  is  soluble  in  five  times  its  volume  of 
water.     It  takes  fire  easily  in  the  air,  burning  with  a  bluish- 
white  flame,  evolving  white  fumes  of  arsenous  oxide.     If 
a  cold  surface  of  porcelain  be  held  in  this  flame,  metallic 
arsenic  is  deposited  upon  it  as  a  dark  stain  or  tache.     Hy- 
drogen arsenide  is  easily  decomposed  when  the  tube  through 


212 


INOlidA M( '  ( 'HEMISTRY. 


which  it  is  passing  is  heated  to  redness,  a  dark  mirror-like 
ring  of  metallic  arsenic  being  formed  just  beyond  the  heated 
spot.  The  gas  is  also  decomposed  when  passed  into  a  solu- 
tion of  silver  nitrate,  forming  arseuous  acid  and  precipitat- 
ing metallic  silver. 

EXPERIMENT. — Marsh's  test  for  arsenic  depends  upon  the  produc- 
tion of  arsine  whenever  arsenic  is  present  in  any  soluble  form  in  a 
solution  in  which  hydrogen  is  being  evolved.  The  form  of  Marsh's 
apparatus  employed  by  the  author  is  represented  in  Fig.  62.  It  con- 
sists of  a  three-necked  bottle,  through  the  middle  tubulure  of  which 
a  funnel-tube  passes  for  the  supply  of  liquid,  while  one  of  the  side 
openings  has  a  siphon  tube  for  withdrawing  the  exhausted  acid,  and 


Fig.  62.  Marsh's  Arsenic  Apparatus. 

the  other  a  delivery  tube  carrying  a  bulb  filled  with  cotton,  to  retain 
impurities  mechanically  carried  over  with  the  gas.  Next  to  this  bottle 
is  ajar  containing  potassium  hydroxide  arid  calcium  chloride  to  purify 
the  gas,  which  then  passes  through  a  long  tube  of  hard  glass  drawn 
out  at  intervals.  Pure  zinc  in  fragments  is  first  put  into  the  three- 
neeked  bottle,  and  then  pure  sulphuric  acid,  previously  diluted  with 
three  parts  of  water  and  cooled,  is  added  until  this  bottle  is  about  one 
third  full.  After  allowing  sufficient  time  for  the  air  to  be  expelled 
from  the  apparatus,  the  narrow  tube  is  heated  to  dull  redness  by  the 
gas  flame.  If  no  dark  deposit  appears  beyond  the  flame  in  fifteen 
minutes,  the  materials  may  be  considered  pure.  The  liquid  suspected 


OXIDES  AND  ACIDS  OF  ARSENIC.  213 

to  contain  arsenic  —  which  must  be  perfectly  free  from  all  organic 
matter — is  now  added  through  the  funnel-tube.  If  arsenic  be  present, 
the  flame  of  hydrogen  burning  at  the  end  of  the  tube  will,  often  in  a 
few  seconds,  change  color,  becoming  whitish,  and  will  deposit  a  dark 
brown  metallic  spot  on  the  porcelain  crucible  cover  pressed  down 
upon  it.  If  the  tube  be  again  heated,  the  arsine  will  be  decomposed 
and  the  arsenic  be  deposited  as  a  dark  metallic  ring.  According  to 
Wormley  ^^  of  a  grain  of  arsenous  oxide  in  one  hundred  grain 
measures  of  the  solution  may  be  detected  by  this  test. 

Hydrogen  arsenide  is  one  of  the  most  active  poisons 
known.  It  should  therefore  be  experimented  upon  with 
the  greatest  care. 

OXIDES   AND   ACIDS    OF   ARSENIC. 

278.  The   oxides   of  arsenic,  with    their   corresponding 
acids,  are  the  following: 

Oxides.  Acids. 

Arsenous  oxide  As2O3  Arsenous  acid  HAsO2 

Arsenic  oxide     As2O5  Arsenic  acid     H3AsO4 

ARSENIC  OXIDE. — Formula  As2O5.     Molecular  mass  229 '6. 

279.  Preparation  and  Properties. — Arsenic  oxide,  ob- 
tained by  heating  arsenic  acid  to  dull  redness,  is  an  opaque, 
white,  amorphous,  deliquescent  mass,  which  fuses  at  a  bright 
red  heat,  and  decomposes  into  arsenous  oxide  and  oxygen. 
By  solution  in  water  it  forms  arsenic  acid. 

ARSENIC  ACID. — Formula  H3AsO4.     Molecular  mass  141*74. 

280.  Preparation  and  Properties.  —  Arsenic  acid  is 
produced  by  oxidizing  arsenous  oxide  or  acid  by  nitric  acid, 
and  evaporating  to  a  syrup.     On  standing,  long  rhomboidal 
laminae  separate,  which  contain  water  of  crystallization  and 
are  deliquescent.     At  100°  this  water  is  expelled,  and  needle- 
shaped  crystals  of  the  acid  H3AsO4  are  produced.     Its  aque- 
ous solution  is  strongly  acid.     On  heating  arsenic  acid  to 
150°,  di-  or  pyro-arsenic  acid,  H4As.,O7,  results;  and  at  200°, 


214  INORGANIC  CHEMISTRY. 

another  molecule  of  water  is  lost  and  meta  -  arsenic  acid, 
HAsO3,  is  obtained.  Salts  corresponding  to  each  of  these 
acids  have  been  produced.  Arsenic  acid  and  its  salts  are 
poisonous,  though  less  so  than  arsenous  compounds. 

ARSENOUS  OXIDE. — Formula  As.,Oa.     Molecular  mu**  197*68. 
Molecular  volume  1  (anomalous).     Relative  density  197 '68. 

281.  Occurrence  and  Preparation. — Arsenous  oxide 
occurs  native  as  the  mineral  arsenolite.     It  is  prepared  by 
roasting  arsenical  ores  with  free  access  of  air,  and  collecting 
the  vapors  in  partitioned  chambers.     The  tine  dust  thus  ob- 
tained is  purified  by  re-sublimation. 

282.  Properties. — Arsenous  oxide  exists  in  two,  prob- 
ably polymeric,  modifications.     When  condensed  at  a  tem- 
perature of  400°,  it  forms  a  transparent  vitreous  mass  «,  of 
specific  gravity  3'738.     When  deposited  slowly  at  tempera- 
tures slightly  less  elevated,  this  variety  crystallizes  in  right 
rhombic  prisms.    The  second  modification,  ft,  is  obtained  by 
condensing  the  vapor  at  200°,  in  brilliant  transparent  octa- 
hedral crystals,  of  specific  gravity  3 -689.     The  same  octahe- 
dral form  is  obtained  on  cooling  a  saturated  aqueous  solu- 
tion.   The  vitreous  or  «  variety  passes  gradually  at  ordinary 
temperatures,  rapidly  at  100°,  into  y9,  forming  a  white  opaque 
mass  resembling  porcelain.    When  the  vitreous  variety  is  dis- 
solved to  saturation  in  hot  hydrochloric  acid  and  left  to  cool 
slowly,  it  crystallizes  in  octahedrons,  the  formation  of  eacli 
crystal  being  accompanied  with  a  flash  of  light.     Arsenous 
oxide  volatilizes  at  218°,  yielding  a  vapor  whose  density  is 
198  instead  of  99.     This  would   indicate  that  the  vitreous 
modification,  which  is  formed  at  high  temperatures,  has  the 
molecular  formula  As4O6,  double  that  of  the  octahedral  mod- 
ification.    Both  varieties  are  soluble  in  water,  in  hydrochlo- 
ric acid,  and  in  alkaline  solutions.    Arsenous  oxide  is  a  most 
energetic  poison,  one  or  two  decigrams  being  sufficient  to 
Destroy  life. 


ANTIMONY. 


215 


EXPERIMENTS. — Arsenous  oxide  may  be  readily  recognized  by  its 
weight,  by  its  volatility,  and  by  its  crystalline  form.  If  a  few  milli- 
grams be  placed  in  a  small  open  tube 
(Fig.  63)  and  heated  over  a  gas-flame — 
the  upper  part  of  the  tube  being  slightly 
warmed  —  the  oxide  will  be  volatilized 
and  the  vapor  will  condense  on  the  tube 
in  a  ring  of  brilliant  octahedral  crys- 
tals like  those  in  Fig.  (34.  If  in  another 
similar  tube  a  mixture  of  arsenous  oxide 

and  a  little  charcoal 

be  placed  and  heat- 
ed,  a   dark   ring   of 

metallic  arsiMiic  will 

be   deposited,  as 

shown  in  the  figure. 

No    other   substance 

but    arsenic    gives 

these  appearances. 


Fig.  64.  Crystals  of 
Arseuous  oxide. 


Fig.  63.  Testing  for  Arsenic. 


The  best  antidote  for  arsenic  is  freshly  prepared  ferric  or 
magnesic  hydrate. 

ARSENOUS  ACID. — Formula  H3AsO.r     Molecular  mass  125 '78. 

283.  Preparation  and  Properties. — When  arsenous 
oxide  is  dissolved  in  water,  an  acid,  styptic  liquid  is  ob- 
tained, which  can  not  be  evaporated  without  decomposition. 
The  arsenites  in  general  are  more  stable,  and  include  both 
ortho-arsenites  and  meta-arsenites.     Potassium  arsenite  is  the 
chief  ingredient  in  Fowler's  solution,  used  in  medicine,  and 
copper  arsenite  in  Paris  green,  used  as  a  pigment. 

ANTIMONY.  —  Symbol  Sb.  Atomic  mass  119 -6.  Valence  III 
andV.  Relative  density  239'2  (?).  Molecular  mass  478 '4  (?). 
Molecular  volume  2.  The  mass  of  1  liter  of  antimony-vapor  is 
21-86  grams  (240  criths)  (?). 

284.  History  and  Occurrence. — Antimony  was  first 
prepared  by  Basil  Valentine  toward  the  end  of  the  fifteenth 


216  INORGANIC  CHEMISTRY. 

century.  It  occurs  in  nature  both  free  and  in  combination. 
The  most  abundant  source  of  it  is  the  sulphide,  known  as 
stibnite ;  but  it  exists  in  combination  with  oxygen  in  the 
minerals  valentinite,  senarmontite,  and  cervantite ;  with  sil- 
ver, in  dyscrasite ;  and  with  silver  and  sulphur  in  pyrargy- 
rite  and  miargyrite. 

285.  Preparation  and  Properties. — Commercial  anti- 
mony is  generally  produced  by  acting  upon  the  melted  native 
sulphide  with  iron,  producing  ferrous  sulphide  and  free  anti- 
mony, according  to  the  equation  : 

Sb&  +  Fe3  =   (FeS)3  +  8b, 

It  is  also  obtained  by  roasting  the  sulphide,  and  then  reduc- 
ing the  oxide  thus  obtained,  with  charcoal.  By  fusion  with 
sodium  carbonate  and  a  small  quantity  of  antimonous  sul- 
phide, the  metal  may  be  obtained  pure. 

Antimony  is  a  brilliant  bluish-white  brittle  metal,  of  spe- 
cific gravity  6*715.  It  crystallizes  in  rhombohedrous,  isomor- 
phous  with  arsenic  and  red  phosphorus.  A  curious  allotropic 
variety  is  obtained  by  electrolysis,  having  a  specific  gravity 
of  5 '8,  and  passing  into  the  ordinary  condition  when  heated 
or  struck,  with  the  evolution  of  great  heat.  Antimony  melts 
at  450°,  and  at  a  white  heat  may  be  distilled.  It  tarnishes 
scarcely  at  all  in  the  air,  but  takes  fire  at  a  red  heat,  pro- 
ducing autimonous  oxide.  It  is  strongly  attacked  by  chlo- 
rine, forming  antimonous  and  antimonic  chlorides,  SbCl, 
and  SbCL.  Antimony  is  used  largely  in  the  arts  as  a  con- 
stituent of  type-metal. 

COMPOUNDS    OF   ANTIMONY. 

286.  Hydrogen  An ti moiiide  or  Stibine,  H3Sb.— 

Whenever  an  antimony  compound  is  present  in  a  solution 
from  which  hydrogen  is  being  evolved,  an  inodorous  gas 
escapes  mixed  with  the  hydrogen,  causing  it  to  burn  with 
a  bluish-white  name.  This  gas  is  stibine.  It  is  analogous 


OXIDES  AM)  STLPHWEfi  OF  ANTIMONY.  'Ill 

to  arsine,  and  is  similarly  decomposed  by  heat ;  but  the  me- 
tallic deposit  of  antimony  is  easily  distinguished  from  that 
of  arsenic  by  its  darker  color,  its  smoky  appearance,  its  less 
volatility,  its  insolubility  in  hypochlorites,  and  its  solubility 
in  ammonium  sulphide. 

287.  Aiitimoiious  and  Antimoiiic  Oxides  and  Acids. 
Antimonic  oxide,  Sb2O5,  is  a  tasteless,  yellowish,  insoluble 
powder,  of  specific  gravity  6 '6,  obtained  by  heating  antimo- 
iric  acid.     Antimonic  acid  is  obtained  by  oxidizing  anti- 
mony by  nitric  acid  or  by  treating  antimonic  chloride  with 
water.     Both  the  ortho-acid,  H5SbO5,  and  the  di-meta  acid, 
HSbO3,  have  been  obtained ;  and  salts  of  di-antimonic  acid, 
H4Sb2O7,  are  also  known. 

Antimonous  oxide,  Sb2O;J),  occurs  native,  in  two  different 
crystalline  forms,  as  senarmontite  and  valentinite.  It  is  the 
product  of  the  combustion  of  antimony  in  the  air,  and  is 
then  crystalline  ;  by  pouring  antimonous  chloride  into  a  boil- 
ing solution  of  sodium  carbonate  it  is  obtained  as  a  dirty- 
white  powder,  which  becomes  yellow  when  heated.  Anti- 
monous acid,  HSbO2,  is  a  feeble  acid,  forming  easily  de- 
composable salts.  It  acts  also  as  a  base,  SbO  or  antimonyl 

acting  as  a  radical.    Thus  tartar-emetic  is  C4H4O2  j  Q/g^Q\ 
potassio-antimonyl  tartrate. 

288.  Antimonous   and  Antimonic   Sulphides   and 
Sulph-acids. — Antimonic  sulphide,  Sb2S5,  is  obtained  as 
a  yellowish-red  powder  by  the  action  of  hydrogen  sulphide 
upon  a  solution  of  the  chloride  in  tartaric  acid,  or  by  acidi- 
fying a  solution  of  an  alkaline  sulph-antimonate.     It  unites 
readily  with  sulphides  of  positive  elements,  forming  sulph- 
antimonates,  having  the  general  formula  M3SbS4 ;  of  which 
sodium  sulph-antimonate,  Na,SbS4,  9  aq. — sometimes  called 
Schlippe's  salt — is  an  example. 

Antimonous  sulphide,  Sb2S3,  exists  native  as  s.tibnite,  as 
above  stated.  It  has  a  steel-gray  color,  a  specific  gravity 


218  ryoRGAyir  CHEMISTRY. 


of  4*5,  and  a  strong  metallic  luster.  It  crystallizes  in  ortho- 
rhombic  prisms.  It  is  thrown  down  by  hydrogen  sulphide 
from  antimonous  solutions  as  a  bright  orange-red  precipitate, 
which  contains  water.  On  fusion  it  becomes  steel-gray.  The 
sulph-antimonites,  which  it  forms  by  union  with  positive  sul- 
phides, are  largely  represented  among  minerals  :  pyrargyrite 
Ag'3SbS3,  and  boulangerite  Pb"3(SbS3)2,  being  ortho-sulph- 
antimonites  ;  miargyrite  Ag'SbS2,  and  berthierite  Fe"(SbS2)2 
being  meta-sulph-antimonites  ;  and  jamesonite  Pb"2Sb2S5,  and 
brongniardite  (PbAg)"2Sb.2S5  being  di-  or  para-sulph-antimo- 
nites. 

§  4.    BISMUTH. 

Symbol  Bi.     Atomic  maw  207  '3.     Valence  III  ami  V  .  •    Specific 
gravity  of  solid  9'83.     Fuse*  at  264°. 

289.  History.  —  Bismuth  was  first  distinctly  recognized 
by  Basil  Valentine  in  the  fifteenth  century.     Agricola,  in 
1529,  calls  it  Bisemutum,  and  Paracelsus   mentions  it  as 
Wisemat.     It  was  for  a  long  time  confounded  with  other 
metals,  especially  with  lead,  tin,  and  antimony.     Pott,  in 
1739,  first  described  its  characteristic  reactions. 

290.  Occurrence  and  Preparation.  —  Bismuth  occurs 
in  the  metallic  state  in  veins  traversing  gneiss,  clay-slate, 
and  other  crystalline  rocks,  principally  in  Saxony  and  Bohe- 
mia.    It  occurs  also  as  oxide,  forming  the  mineral  bismite  ; 
as  sulphide,  or  bismuthinite  ;  as  sulpho-telluride,  or  tetrady- 
mite  ;  and  as  carbonate,  or  bismutite.     It  is  prepared  on  the 
large  scale  in  the  arts  from  the  native  bismuth  by  placing 
this,  mixed  with  the  rocky  gangue,  in  iron  tubes,  slightly 
inclined,  which  are  heated  in  a  furnace.    The  bismuth  melts 
and  flows  out  at  the  lower  ends  of  the  tubes  into  suitable 
vessels,  from  which  it  is  ladled  into  moulds.     The  bismuth 
of  commerce  contains  arsenic,  iron,  and  other  metals,  from 
which  it  may  be  freed  by  fusion  with  potassium  nitrate,  by 


PROPKRT/ES  OF  lifSUt'TH.  210 

which  these  metals  are  oxidized.     Chemically  pure  bismuth 
may  be  obtained  by  reducing  the  basic  nitrate  by  charcoal. 

291.  Properties.  —  Bismuth  is  a  hard,  brittle,  brilliant 
reddish-white  metal.     It  is  powerfully  dia-niagnetic,  and  has 
a  strong  tendency  to  crystallize  when  cooled  from  fusion  ; 
by  melting  a  considerable  quantity  of  it,  allowing  it  to  cool 
until  a  crust  forms  on  the  surface,  piercing  this  and  pour- 
ing out  the  metal  which  still  remains  fluid,  crystals  of  great 
size  and  beauty  may  be  obtained.     They  are  rhombohedrons, 
though  on  account  of  the  large   interfacial  angle,  87°  40', 
they  have  often  been  mistaken  for  cubes,  in  which  this  angle 
is  90°.     Owing  to  a  slight  superficial  oxidation,  these  crys- 
tals, as  usually  obtained,  are  beautifully  iridescent.    Bismuth 
has  a  specific  gravity  of  9*83 ;  it  melts  at  264°,  and  expands 
one  thirty-second  of  its  bulk  on  solidifying.     It  may  be  dis- 
tilled at  a  white  heat.     It  is  unaltered  in  dry  air,  but  is  tar- 
nished in  presence  of  moisture.     Strongly  heated,  it  takes 
fire,  burning  with  a  bluish-white  flame,  and  forming  bismu- 
thous  oxide.     Chlorine  and  nitric  acid  attack  it  readily,  but 
hydrochloric  and  sulphuric  acids,  when  cold,  have  no  action 
upon  it. 

Bismuth  is  used  in  the  arts  for  forming  alloys.  Hose's 
fusible  metal  is  composed  of  one  part  of  lead,  one  of  tin,  and 
two  of  bismuth;  it  melts  at  94°.  Lippwitz's  fusible  metal 
contains  three  parts  of  cadmium,  four  of  tin,  eight  of  lead, 
and  fifteen  of  bismuth;  it  melts  at  60°.  An  alloy  of  lead 
and  bismuth  is  used  in  the  so-called  permanent  metallic 
pencils. 

COMPOUNDS   OF   BISMUTH. 

292.  Bismuthous  Chloride,  BiCl3. — This  chloride  may 
be  formed  by  the  direct  action  of  chlorine  upon  bismuth. 
It  is  a  white,  granular,  deliquescent   substance,  fusible  at 
230°  and  volatile  at  435°.     By  contact  with  water  it  is  de- 
composed, forming  bismuthyl  chloride,  (BiO)Cl,  sometimes 
called  bismuth  oxychloride. 


220  lyORG.lXIC  CHEMISTRY. 


293.  Bismuthic  Oxide,  Bi.,O5.  —  Bismuthic  oxide  is  ob- 
tained by  heating  its  hydrate  to  130°.    It  is  a  brown  powder, 
which  gives  up  a  part  of  its  oxygen  readily.     Its  hydrate, 
called  bismuthic  acid,  HBiO3,  may  be  prepared  by  oxidiz- 
ing bismuthous  hydrate,  suspended  in  water,  by  a  current 
of  chlorine.     It  is  a  bright  red  powder,  which  loses  oxygen 
a  little  above  100°.     Its  salts  are  called  bismuthates  ;  po- 
tassium  bismuthate,   KBiO,,    and    bismuthous    bismuthate, 
Bi'"BivO4,  are  examples. 

294.  Bismuthous  Oxide,  Bi2O,.  —  This  oxide  occurs 
native  as  bismite.     It  may  be  formed  by  burning  the  metal 
in  air,  or  by  igniting  the  hydrate,  carbonate,  or  nitrate.     It 
is  a  pale-yellow  powder,  of  specific  gravity  8  '2,  which  melts 
at  a  red  heat,  and  is  insoluble  in  water.     It  has  been  ob- 
tained  in  ortho  -  rhombic    prisms.      Bismuthous    hydrate, 
H3BiO,,  is  obtained  by  treating  a  bismuthous  salt,  as  the 
chloride,  for  example,  with   potassium  hydrate.     A  white, 
flocculent  precipitate  is  thrown  down,  which  on  drying  loses 
water  and  becomes   an  amorphous  white    powder,  HBiO.r 
With  strong  bases  this  body  acts  like  an  acid,  sodium  bis- 
muthite,  NaBiO.2,  being  one  of  its  salts.     But  with  strong 
acids,  on  the  other  hand,  this  hydrate  is  strongly  basic,  the 
nitrate,  Bi(NO3)3,  the  sulphate,  Bi,(SO4)3,  the  carbonate, 
Bi.2(CO3)3,  and  the   phosphate,  BiPO4,  being   well-known 
compounds.     By  pouring  the  nitrate  into  a  large  quantity 
of  water,  the  mono  -meta-nitrate,  BiNO4,  is  produced. 

Bismuthous  sulphide,  Bi2S3,  occurs  native  as  bismuthiu- 
ite.  It  is  obtained  as  a  black  precipitate,  on  adding  hydro- 
gen sulphide  to  solutions  of  bismuth  ;  but,  unlike  the  sul- 
phides of  arsenic  and  antimony,  it  is  not  soluble  in  solutions 
of  the  alkali  sulphides.  It  forms  with  metallic  sulphides 
salts  called  sulpho-bisrnuthites,  some  of  which,  as  that  of 
lead  or  kobellite,  Pb"3(BiS3)2,  and  those  of  copper,  called 
emplectite,  Cu"(BiS2)2,  and  wittichenite,  Cu"3(BiS3)2,  occur 
native. 


RELATIONS  OF  THE  \LTff (tfi A'.V  C.ROrr.  221 

§  5.    RELATIONS  OF  THE  NITROGEN  GROUP. 

295.  The  members  of  the  nitrogen  group  have  close 
relations,  both  physically  and  chemically,  with  each  other. 
From  nitrogen  to  bismuth  they  increase  in  density  and  in 
atomic  mass,  while  their  chemical  activity  decreases  in  the 
same  order.  The  last  four  are  iso-dimorphous  ;  that  is,  they 
all  have  two  crystal-forms,  which  are  the  same  for  each  sub- 
stance. A  comparison  of  their  compounds  will  show  how 
closely  they  are  allied  chemically : 

TRIAD  COMPOUNDS. 

Hydrides.  Chlorides.  Oxides.  Sulphides. 

N               H,N  NC13               NA 

P                H3P  PC13               PA               P2S3 

As               H3As  AsCl3              As2O3              As2S3 

Sb              K5Sb  SbCl3              SbA             Sb2S;! 

Bi  BiCl3              BiA               Bi2S3 

PENTAD  COMPOUNDS. 

Chlorides.  Oxides.  Sulphides. 

N  N.A 

p          PCI,  PA          PA 

As                 AsCl5  As2O5  As2S5 

Sb                 SbCl5  Sb2O5  Sb2S5 

Bi  Bi205 


222 


EXERCISES. 

§!• 

1.  In  what  ways  may  nitrogen  be  prepared? 

2.  The  mass  of  a  given  volume  of  oxygen  is  thirty  grams ;  what 
is  the  mass  of  the  same  volume  of  nitrogen  ? 

3.  What  mass  of  oxygen  does  a  cubic  meter  of  air  contain  ? 

4.  What  are  the  proofs  that  air  is  merely  a  mixture? 

5.  What  volume  of  air  is  required  to  yield  six  kilograms  of  oxygon  ? 

6.  At  what  temperature  has  air  the  density  of  H  at  0°? 

7.  What  mass  of  nitrogen  does  ten  grams  of  ammonia  contain? 

8.  A  liter  of  water  is  to  be  saturated  with  ammonia- gas  at  0°;  how 
many  grams  of  (NHJC1  and  of  CaO  must  be  used  in  the  process? 

9.  What  volume  of  H3N  at  15°  will  a  kilogram  of  NH4C1  yield? 

10.  250  cubic  centimeters  ammonia  decomposed  by  el •'(•trie  sparks 
gives  what  volume  of  mixed  gases?    If  200  cubic  centimeters  of  oxy- 
gen  be  added  and  exploded,  what  will  be  the  composition   of  the 
remaining  gas? 

11.  What  volume  of  NH:i  will  neutralize  a  liter  of  HC1? 

12.  How  much  nitric  acid  may  be  obtained  from  a  kilogram  KNO., 
by  the  laboratory  process?     How  much  by  the  commercial  ? 

13.  To  neutralize  ten  grams  MgO  requires  how  many  cubic  centi- 
meters of  nitric  acid  of  specific  gravity  142?     (Acid  contains  70  per 
cent  of  HNO3,) 

14.  Write  the  graphic  formula  of  nitrogen  tetr-oxide? 

15.  A  kilogram  of  copper  gives  what  volume  of  N2O2? 

16.  One  liter  of  N2O2  requires  what  volume  of  oxygen  to  make 

NA? 

17.  How  many  cubic  centimeters  of  O  and  of  N  in  one  liter  of 
nitrogen  di-oxide? 

18.  Fifteen  grams  ammonium  nitrate  yield  what  volume  of  N2O? 

19.  What  volume  of  H  will  one  gram  of  K2O  burn?     One  liter? 

20.  One  cubic  centimeter  of  liquefied  N2O  requires  what  mass  of 
(NH4)NOa? 

§2. 

21.  Give  the  chemical  stages  in  making  phosphorus. 

22.  One  hundred  kilograms  of  bone-ash,  80  per  cent  calcium  phos- 
phate, yield  how  many  kilograms  of  phosphorus? 


EXERCISES.  223 

23.  How  do  common  and  allotropic  phosphorus  differ? 

24.  One  liter  of  phosphine  contains  what  volume  of  P  vapor? 

25.  What  volume  of  air  is  required  to  burn  ten  grams  of  P? 

26.  If  dissolved  in  boiling  water,  how  much  phosphoric  acid  would 
the  above  product  yield  ? 

§3. 

27.  Give  the  preparation  and  properties  of  metallic  arsenic. 

28.  Describe  Marsh's  test.    What  is  the  limit  of  its  delicacy? 

29.  At  a  certain  temperature  the  mass  of  100  liters  of  hydrogen  is 
four  grams ;  what  will  be  the  mass  of  this  volume  of  As  vapor  at  the 
same  temperature  ? 

30.  H3As  contains  \vhat  volume  of  H  ?     How  much  air  is  required 
to  burn  it  ? 

31.  Calculate  the  percentage  of  antimony  in  antimonous  sulphide. 

32.  How  is  stibine  distinguished  from  arsine? 

33.  Give  the  formulas  of  the  common  antimony  compounds. 


224  ixona  t  i  \K '  ( -it  KM  is  77,'  r. 


CHAPTER  FIFTH. 

NEGATIVE  TETRADS. 

§  1.    CARBON. 

Symbol  C.  Atomic,  ma.s,s  11 '97.  Valence  II  and  IV.  Relative 
density  12  (?).  Molecular  maw  23'94  (?).  Molecular  rol- 
tnne  2.  The  mass  of  1  liter  of  carbon-vapor  i«  1*075  gram* 
(12  mtfi,s)  (?). 

296.  Occurrence.  —  Carbon  occurs  native  in  two  allo- 
tropic  forms,  known  as  the  diamond  and  as  graphite.     Also 
more  or  less  impure,  in  the  various  forms  of  mineral  coal. 
Combined  with  hydrogen,  it  occurs  in  bitumen  and  petro- 
leum ;  with  oxygen,  it  exists  in  the  air ;  and  with  oxygen 
and  calcium  it  forms  limestone,  a  very  abundant  rock,  of 
which  twelve  per  cent  is  carbon.     It  is  an  essential  constit- 
uent too  of  all  animal  and  vegetable  tissues. 

297.  Properties. — I.  As  DIAMOND. — The  form  of  carbon 
known  as  the  diamond  is  a  brilliant,  transparent,  and  gen- 
erally colorless  solid,  having  a  specific  gravity  of  3 *5,  and 
crystallizing  in  forms  belonging  to  the  isometric  system  (Fig. 
65),  the  faces  being  often  rounded.     It  does  not  conduct  heat 
or  electricity,  and  has  a  very  high  refractive  and  dispersive 
power.    It  is  the  hardest  form  of  matter  known.     Heated  to 
a  high  temperature,  it  is  converted  into  a  black  mass  resem- 
bling  graphite.      Lavoisier  established   its  composition   in 
1776  by  burning  it  in  oxygen. 

The  diamond  occurs  generally  in  the  form  of  small  rounded 
pebbles  in  alluvial  detritus  produced  by  the  disintegration 
of  ancient  rocks,  from  which  it  is  obtained  by  washing.  The 


DIAMOND  AND  GRAPHITE. 


chief  localities  are  India,  Borneo,  South  Africa,  and  Brazil ; 
though  a  few  diamonds  have  been  found  in  Georgia  and 
North  Carolina  in  this  country.  It  is  cut  for  a  gem  into 


Fig.  65.  Crystalline  forms  of  Diamond. 

forms  having  a  relation  to  its  directions  of  cleavage — known 
as  the  brilliant,  the  rose,  and  the  table — by  means  of  dia- 
mond dust. 

II.  As  GRAPHITE. — The  second  form  of  carbon,  known 
as  graphite,  is  a  friable,  leaden-gray  solid,  unctuous  to  the 
touch,  of  specific  gravity  2  to  2*2,  and  crys- 
tallizes in  hexagonal  plates  (Fig.  66).  It 
has  a  semi -metallic  luster,  conducts  heat 
and  electricity  readily,  and  is  combustible 
with  difficulty,  leaving  generally  a  few  per 
cents  of  ash.  It  is  soluble  in  melted  iron, 
from  which  it  crystallizes  on  cooling.  Ni- 
tric acid  mixed  with  potassium  chlorate, 
when  heated,  oxidizes  graphite  to  graph- 
itic acid. 

Graphite  occurs  both  foliated  and  massive,  in  metamor- 
phic  rocks,  in  England,  Siberia,  and  Ceylon,  and  in  various 
localities  in  the  United  States;  as  Sturbridge,  Mass.,  Ticon- 
deroga,  N.  Y.,  Brandon,  Yt.,  Wake,  N.  C.,  etc.  It  is  puri- 
fied by  Brodie's  process,  by  treating  it  .with  potassium  chlo- 
rate and  nitric  acid  ;  and  is,  after  drying,  condensed  to  a 
solid  block  by  hydrostatic  pressure.  It  is  largely  used  for 
making  pencils  —  the  name  graphite  coming  from  7y>«f«>,  I 
write — and  also  for  crucibles. 


Fig.  66.  Form  of 
Graphite  Crystal. 


226  INORGANIC  CHEMISTET. 

III.  As  MINERAL  COAL. — The  purest  variety  of  carbcm  in 
the  form  of  mineral  coal  is  that  known  as  anthracite.  It  is 
an  amorphous,  hard,  lustrous,  black  solid,  difficultly  combus- 
tible, and  consisting  of  from  80  to  94  per  cent  carbon.  Its 
specific  gravity  varies  from  1*3  to  1*7.  From  this  there  is 
a  regular  gradation  through  cannel  and  bituminous  coals 
of  all  varieties^to  lignite  or  brown  coal,  which  in  some  cases 
is  scarcely  altered  wood.  All  coal  is  derived  from  primitive 
vegetation,  changed  and  consolidated  by  heat  and  pressure. 
Anthracite  coals  are  found  where  the  strata  have  been  most 
heated  or  disturbed,  bituminous  where  they  remain  nearly  or 
quite  horizontal ;  while  brown  coal  or  lignite  is  more  recent 
in  age,  being  generally  tertiary. 

Other  varieties  of  more  or  less  pure  carbon  are :  gas- 
carbon  or  plumbagine,  deposited  in  the  cast-iron  retorts  in 
which  coal-gas  is  made ;  a  hard,  compact,  mammillated  va- 
riety, being  almost  metallic  in  appearance,  and  conducting 
both  heat  and  electricity.  Specific  gravity  1'76.  Vegeta- 
ble coal  or  charcoal,  prepared  on  the  large  scale  by  burning 
wood  in  heaps,  as  shown  in  Fig.  G7,  and  for  special  purposes, 


Fig.  67.  Interior  of  Charcoal  Heap. 

in  iron  cylinders ;  a  bluish-black,  porous  substance,  retaining 
minutely  the  form  of  the  original  wood,  and  having  a  spe- 
cific gravity  of  1*7.  Animal  coal  or  bone-black,  obtained 
by  igniting  bones  in  close  vessels;  also  a  black  porous  mass, 


ABSOEPTIOX  BY  CHARCOAL. 


227 


containing  90  per  cent  of  calcium  phosphate.  And  lamp- 
black, or  soot,  prepared  by  collecting  the  matters  condensed 
from  the  smoke  of  highly  carbonized  bodies,  such  as  pitch 
and  tar,  in  stone  chambers ;  a  soft,  finely  divided,  and  very 
impure  form  of  carbon,  used  in  printing-ink  and  as  a  pig- 
ment. It  always  contains  more  or  less  hydrogen. 

In  all  its  forms,  carbon  is  infusible  and  non-volatile.  As 
vegetable  and  animal  coal,  owing  to  its  very  great  porosity — 
a  single  cubic  centimeter  of  box- wood  charcoal  exposing  a 
surface  of  more  than  four  square  meters — carbon  exhibits  a 
remarkable  power  of  absorbing  gases.  Thus,  box-wood  char- 
coal will  absorb  90  volumes  of  ammonia  gas,  and  that  made 
from  the  shell  of  the  cocoanut,  171  volumes.  From  this  fact 
— i.  e. ,  that  charcoal  carries  within  it  a  condensed  mass  of 
the  oxygen  of  the  air  in  which  it  cooled — it  acts  as  an  ener- 
getic disinfectant  by  oxidizing  foul  vapors.  For  the  same 
reason  animal  charcoal  is  largely  used  as  a  decolorizing  agent, 
particularly  in  refining  sugar.  It  has  been  proposed  for  fill- 
ing respirators,  which  are  placed  over 
the  mouth  to  absorb  noxious  gases. 

Charcoal   filters    are 

also  in  use. 

EXPERIMENTS. — The 
powerful  absorption  of 
ammonia  gas  by  char- 
coal may  be  shown  by 
filling  a  cylinder  over 
mercury  with  the  dry 
gas  (Fig.  68),  and  then 
introducing  into  it  a 
piece  of  cocoanut  char- 
coal, previously  heated 
to  redness  in  sand,  and 

allowed  to  cool  away  from  the  air.  The  ammonia  will  be  rapidly 
absorbed  by  the  charcoal,  and  the  mercury  will  rise  in  the  tube. 

To  show  the  decolorizing  property  of  charcoal,  place  in  four  na.sk.s 
dilute  solutions  of  indigo,  cochineal,  iodide  of  starch,  and  potassium 


Fig.  68.  Absorp- 
tion of  Gases  by 
Charcoal. 


Fig.  69.   Decolorizing  power 
of  Charcoal. 


228  INORGANIC  CHEMISTRY. 

permanganate.  Agitate  each  solution  with  recently  ignited  bone- 
black,  and  throw  each  upon  a  separate  filter  (Fig.  69).  The  liquors 
as  they  run  from  the  funnels  will  be  colorless.  If  beer  or  ale  be  thus 
treated,  it  will  lose  not  only  its  color,  but  also  its  bitter  taste. 

Carbon  is  apparently  unalterable  in  the  air  at  ordinary 
temperatures.  Charred  piles  driven  by  the  Britons  to  pre- 
vent Julius  Csesar  from  crossing  the  Thames,  and  wheat 
charred  nearly  2,000  years  ago  at  Herculaneuni,  are  yet 
unchanged.  When  heated  in  the  air,  it  burns,  forming  the 
di-oxide.  Heated  with  sulphur,  or  used  to  give  the  electric 
arc  in  hydrogen,  it  unites  directly  with  these  substances, 
forming  carbon  disulphide  and  acetylene. 

CARBON    AND    HYDROGEN. 

298.  Hydrocarbons.  —  The  compounds  of  carbon  and 
hydrogen  —  called  hydrocarbons  —  are  very  numerous,  and 
are  usually  classified  in  series.     Most  of  them  are  more  sat- 
isfactorily considered  in  Organic  Chemistry.     Only  three  of 
them  will  therefore  be  described  here.     These  are  hydrogen 
carbide,  H4C,  hydrogen  di-carbide,  HtC2,  and  di- hydrogen 
di-carbide  H.2C2. 

HYDROGEN  CARBIDE,  OR  METHANE. — Formula  H4C.  Molec- 
ular mass  15 '97.  Molecular  volume  2.  Relative  density  8. 
The  mass  of  one  liter  is  0*716 
grams  (8  criths). 

299.  Occurrence.  —  Meth- 
ane occurs  free  in  nature,  being 
produced  somewhat  abundantly 
by  the  decomposition  of  vegeta- 
ble matter  confined  under  wa- 
ter.    It  constitutes  75  per  cent 
of  the  gas  which  rises  when  the 

bottom  of  a  pond  covered  with      Fie- 70  collection  of  Marsh -gas. 
vegetable  matter  is  stirred  with  a  stick,  whence  it  is  often 
called  marsh-gas.     It  often  escapes  from  seams  in  coal  mines, 


PREPARATION  OF  METHANE. 


229 


and  constitutes  the  fire-damp  of  miners.  It  often  occurs 
largely  in  the  vicinity  of  salt-wells,  as  in  Kanawha,  West 
Virginia.  It  constitutes  nearly  the  whole  of  the  so-called 
natural  gas  which  has  come  so  extensively  into  use  in  some 
of  the  western  cities  for  purposes  of  heating  and  lighting. 

3OO.  Preparation. — Marsh-gas  may  be  obtained  by  fill- 
ing a  bottle  with  \vater,  attaching  a  funnel  to  its  mouth  by 
a  string,  as  shown  in  Fig.  70,  and  inverting  it  in  a  pond  so 
as  to  catch  the  bubbles  which  rise  on  stirring  the  mud  at  the 
bottom.  By  agitating  it  with  a  little  lime-water,  it  may  be 
purified  for  experiment. 

Methane  may  be  also  procured  by  heating  potassium  ace- 
tate in  presence  of  a  strong  base,  usually  potassium  or  sodium 
hydroxide.  The  reaction  which  takes  place  is  as  follows : 

CH3  Na 

Sodium  acetate.       Sodium  hydroxide.       Sodium  carbonate.        Methane. 

EXPERIMENT. — For  the  preparation  of  methane,  two  parts  crys- 
tallized sodium  acetate,  two  parts  sodium  hydroxide,  and  three  parts 


Fig.  71.  Preparation  of  Hydrogen  carbide. 

powdered  quick-lime  are  intimately  mixed  together  and  heated  in 
a  thin  copper  or  iron  flask  to  bright  redness  (Fig.  71).     The  lime  is 

16 


230 


INORGANIC  CHEMISTRY. 


used  to  prevent  the  fusion  of  the  mass.  The  gas  is  rapidly  evolved, 
and  may  be  collected  over  water. 

3O1.  Properties. — Hydrogen  carbide  is  a  colorless,  odor- 
less, and  tasteless  gas,  and  is  but  slightly  soluble  in  water. 
Its  critical  temperature  is  —81 '8°  and  critical  pressure  54'9 
atmospheres.  Reducing  the  pressure  to  one  atmosphere,  the 
temperature  of  the  liquid  sinks  to  —164°,  which  is  therefore 
its  boiling  point.  At  this  temperature  the  liquid  methane 
has  a  density  of  0*415.  It  is  the  lightest  gas  next  to  hy- 
drogen, its  specific  gravity  being  0'5576.  It  is  combustible, 
burning  in  the  air  with  a  pale,  faintly  luminous  flame.  By 
passing  electric  sparks  through  the  gas,  it  is  decomposed, 
and  yields  twice  its  volume  of  hydrogen.  It  forms  an  ex- 
plosive mixture  with  two  volumes  of  oxygen  or  ten  volumes 
of  air,  and  is  the  cause  of  the  serious  coal-mine  explosions 
which  sometimes  happen  in  coal  districts.  By  the  action  of 
chlorine,  its  hydrogen  is  gradually  replaced  by  this  element, 
forming  successively  the  compounds  CH:iCl,  CH,CLj,  CHCl.^, 
and  CC14. 

Methane  constitutes  the  first  member  of  a  homologous 
series  of  hydrocarbons  known  as  the  marsh-gas  series,  the 
successive  members  increasing  uniformly 
by  CH.,.  They  are  all  saturated  substances, 
having  the  general  formula  CnH2n+2 ;  i.  e., 
they  contain  twice  as  many  atoms  of  hy- 
drogen as  of  carbon,  plus  two.  They  con- 
stitute the  essential  portion  of  the  various 
native  petroleums.  The  second  member  of 
the  series  is  ethane,  C2H0,  or  H;JC — CH,. 

EXPERIMENT. — The  levity  and  inflammabil- 

Fig.  72.  Combustibility    ity  of  this  gas  may  be  shown,  as  in  the  case  of 
of  Marsh-gas.  J  °    .        J       .  ' 

hydrogen,  by  introducing  a  lighted  taper  into  a 

jar  of  it,  held  mouth  downward.  The  gas  will  burn  at  the  mouth 
of  the  jar,  and  the  candle-flame,  as  it  passes  up  into  it,  will  be  extin- 
guished. 


PREPARATION  AM)  PROPERTIES  OF  ETRYLEXE.    231 

HYDROGEN  DI-CARBIDE  OR  ETHYLENE. — Formula  H4C2,  or 
H2C  =  CH2.  Molecular  mass  27*94.  Molecular  volume  2. 
Relative  density  13 '97.  The  mass  of  one  liter  is  1'25  grams 
(14  criths). 

302.  History. — Ethylene  was  discovered  ID  1796  by  four 
Dutch  chemists,  Deiman,  Paets  van  Troostwyk,  Bondt, 
and  Lauwerenburgh.     It  has  been  found  in  small  quantity 
among  the  gases  of  coal-mines. 

303.  Preparation. — It  is  usually  prepared  by  the  action 
of  sulphuric  acid  upon  alcohol,  according  to  the  reaction : 

C2H60  =  HA  +  H20 

This  equation  exhibits  only  the  final  result ;   the  chemical 
change  itself  is  evidently  more  complicated. 

EXPERIMENTS. — To  prepare  etbylene,  one  volume  of  alcohol  and 
four  volumes  of  sulphuric  acid  are  mixed  in  a  flask  with  sand  to  a 
thick  paste,  and  gently  heated.  The  sand  is  added  to  prevent  froth- 
ing toward  the  end.  The  gas  may  be  purified  by  passing  it  through 
milk  of  lime  to  remove  sulphurous  oxide,  and  through  strong  sul- 
phuric acid  to  retain  the  vapors  of  ether  and  alcohol. 

Mitscherlich's  continuous  process  consists  in  passing  the  vapor  of 
80  per  cent  alcohol  through  boiling  dilute  sulphuric  acid — three  parts 
of  water  to  ten  of  acid. 

304.  Properties.  —  Hydrogen  di-carbide  is  a  colorless, 
irrespirable  gas,  having  usually  an  ethereal  odor.     Its  spe- 
cific gravity  is  0'978.     The  critical  temperature  of  ethylene 
is  10*1°,  and  its  critical  pressure  51  atmospheres.     Under 
760  millimeters  pressure  its  temperature  is  —103°,  which 
is  therefore  its  boiling  point.     At  9 '8  millimeters  pressure 
its  evaporation  produces  a  temperature  of  — 150'4°.     Hence 
liquid  ethylene  is  much  used  to  produce  cold  in  the  liquefac- 
tion of  gases.     It  is  soluble  in  about  eight  times  its  volume 
of  water.     It  is  readily  combustible,  burning  in  the  air  with 
a  brilliant  white  flame,  evolving  much  smoke.     Mixed  with 
three  volumes  of  oxygen,  it  explodes  violently  on  the  approach 
of  a  flame.    It  is  decomposed  by  the  electric  spark,  the  carbon 


232  INORGANIC  CHEMISTRY. 

being  deposited,  and  twice  its  volume  of  hydrogen  remaining. 
It  is  an  unsaturated  substance,  and  unites  directly  with  an 
equal  volume  of  chlorine,  forming  an  oily  liquid,  ethylene 
chloride,  C.2H4C12.  From  this  fact  the  gas 
received  from  its  discoverers  the  name 
"  olefiant  gas,"  and  the  liquid  was  called 
the  "  oil  of  the  Dutch  chemists." 

EXPERIMENT. — To  show  the  direct  union  of 
ethylene  and  chlorine,  fill  a  glass  cylinder  half 
full  of  chlorine  over  the  water-cistern,  and  then 
add  rapidly  an  equal  volume  of  olefiant  gas.  The 
gaseous  mixture  will  at  once  begin  to  diminish 
in  volume  (Fig.  73),  oily  drops  will  collect  upon 
Fig.  73.  Formation  of  the  walls  of  the  vessel,  and,  sinking  through  the 
[de<  liquid,  form  a  layer  upon  the  bottom  of  the  con- 
taining cistern.  By  pouring  off  the  water  and  agitating  with  sodium 
carbonate  solution,  the  ethylene  chloride  may  be  purified  and  its  agree- 
able, chloroform-like  odor  obtained. 

Dl-HYDROGEN    Dl-CARBIDE    OR   ACETYLENE. — Formula   H2C2 

or  HC-ECH.  Molecular  mass  25 '94.  Molecular  volume  2. 
Relative  density  12*97.  The  mass  of  one  liter  is  1*16  grams 
(13  criths). 

305.  History  and  Preparation.  —  Acetylene  was  dis- 
covered by  E.  Davy  in  1836,  and  studied  by  Berthelot  in 
1860.     It  may  be  prepared  by  the  direct  union  of  its  constit- 
uents.    When  the  carbon  points  terminating  the  electrodes 
of  a  powerful  voltaic  battery  or  dynamo-machine  are  brought 
together  in  an  atmosphere  of  hydrogen,  the  carbon  and  hy- 
drogen combine  at  the  elevated  temperature  produced  and 
form  acetylene.     It  is  also  a  product  of  the  action  of  heat 
upon  substances  rich  in  carbon  and  hydrogen,  and  is  always 
formed  in  the  imperfect  combustion  of  hydrocarbon  com- 
pounds, such  as  coal-gas. 

306.  Properties. — Acetylene  is  a  colorless  gas,  having 
a  peculiar  and  disagreeable   odor,  and  is  condensable  to  a 


JL L I 'MIXA  TL\(i   (',.( X.  233 

liquid  under  a  pressure  of  68  atmospheres  at  37°,  its  critical 
temperature.  It  has  a  specific  gravity  of  0'92,  is  quite  solu- 
ble in  water,  and  burns  with  a  bright  but  very  smoky  flame. 
It  is  readily  absorbed  by  ammoniacal  cuprous  chloride,  form- 
ing a  red  precipitate  of  cuprous  acetylide,  which  is  explosive. 
This  explosive  body  is  sometimes  formed  in  brass  gas-pipes 
by  the  action  upon  them  of  the  acetylene  in  coal-gas,  and 
has  been  the  cause  of  fatal  accidents.  It  unites  directly  with 
the  halogens,  the  compounds  of  chlorine  with  it,  for  example, 
being  C2H,C12  and  C2H2Clr 

ILLUMINATING   GAS. 

307.  History. — The  production  of  a  combustible  gas 
from  coal  was  first  observed  by  Clayton  in  1664 ;  but  it  was 
not  until  1792  that  Murdock  made  gas-illumination  a  prac- 
tical success.     In  1798  he  lighted  in  this  way  Boulton  and 
Watt's  works  at  Soho,  near  Birmingham.   The  streets  of  Lon- 
don were  first  lighted  with  gas  in  1812.    Gas  was  introduced 
into  Paris  in  1815. 

308.  Preparation. — Illuminating  gas  is  ordinarily  pre- 
pared by  distilling  bituminous  coal  at  a  high  temperature ; 
although  various  other  substances,  such  as  oil,  rosin,  wood, 
and  petroleum  have  also  been  employed  for  its  preparation. 
The  complete  apparatus  for  the  manufacture,  purification, 
and  collection  of  coal-gas  is  represented  in  Fig.  74.    The  coal 
is  placed  in  semi-cylindrical  iron  retorts,  C,  set  in  a  furnace 
shown  upon  the  right,  their  mouths  being  closed  by  heavy 
plates.     Usually  five  retorts  are  heated  by  the  same  fire, 
forming  what  is  technically  called  a  "bench."    The  products 
of  the  distillation  pass  from  the  retorts  through  a  tube  near 
its  mouth,  up  into  a  larger  horizontal  tube,  B,  called  the 
hydraulic  main,  where  the  tar  and  a  portion  of  the  water 
are  condensed  to  liquids  ;  the  gas  then  passes  on,  first  through 
a  series  of  vertical  pipes,  D,  and  then  through  the  coke-box 
or  "scrubber"  O,  by  which  it  is  still  further  cooled  and  the 


234 


IXOL'GA XK'  CHEMISTST. 


COMPOSITION  OF  COAL-GAS.  235 

condensable  vapors  separated.  It  then  enters  the  purifier, 
M,  a  large  metallic  box  containing,  on  shelves  for  the  pur- 
pose, either  dry  slaked  lime  or,  what  is  preferable,  ferric  hy- 
drate, either  alone  or  mixed  with  lime  and  sawdust.  From 
this  it  issues,  freed  from  most  of  its  impurities,  particularly 
sulphur  compounds  and  carbon  di-oxide,  and  is  collected  in 
the  adjoining  gasometer,  G,  for  distribution. 

EXPERIMENT. — The  manufacture  of  coal-gas  may  be  illustrated  on 
the  lecture-table  by  the  apparatus  shown  in  Fig.  75.  The  coal  is  placed 
in  the  retort  upon  the  right,  which  is  then,  heated  by  the  gas-burner. 
The  water  and  volatile  liquid  products  condense  in  the  receiver,  while 
the  gas  passes  on  to  the  first  U-tube,  in  one  limb  of  which  a  piece  of 
red  litmus-paper  is  placed  —  to  detect  ammonia  —  and  in  the  other  a 


Fig.  75.  Distillation  of  Coal. 

a  strip  of  paper  moistened  with  a  solution  of  lead  acetate — to  detect 
hydrogen  sulphide — and  then  to  the  second,  the  bend  of  which  con- 
tains lime-water— which  indicates,  by  becoming  milky,  the  presence 
of  carbon  di-oxide — and  is  finally  collected  over  water  in  the  capped 
receiver.  By  depressing  this  receiver  in  the  water,  and  opening  the 
cock,  the  gas  may  be  lighted  as  it  issues  from  the  jet. 

3O9.  Composition  and  Properties. — Coal-gas  is  a  mix- 
ture of  several  gaseous  products  which  vary  according  to  the 
quality  of  coal  used,  the  temperature  at  which  it  is  distilled, 
etc.,  but  which  consist  essentially  of  hydrogen  and  methane 
(marsh -gas)  mixed  with  variable  proportions  of  ethylene, 
acetylene,  carbon  monoxide  and  di-oxide,  butylene,  nitro- 
gen, oxygen,  and  hydrogen  sulphide.  The  amount  of  gas 
obtained  varies,  with  different  coals,  from  8,000  to  15,000 
cubic  feet  to  the  ton.  Coal-gas  has  a  specific  gravity  vary- 


236  INORGANIC  CHEMISTRY. 

ing  from  0*65  to  0*34.  The  illuminating  power  of  a  gas  is 
determined  by  an  instrument  called  a  photometer,  in  which 
the  amount  of  light  given  by  the  gas,  burning  from  a  jet  at 
the  rate  of  five  cubic  feet  per  hour,  is  compared  with  that 
emitted  by  a  standard  candle  burning  120  grains  of  sperma- 
ceti in  the  same  time.  A  gas  may  rise  in  illuminating  power 
to  25  or  30  candles ;  but  the  average  supplied  in  our  cities 
is  16  candles.  By  heating  the  gas  before  it  is  burned,  Sie- 
mens showed  that  five  feet  of  gas  may  be  made  to  give  a  light 
of  40  to  50  candles. 

The  collateral  products  of  the  coal-gas  manufacture  are  in 
general,  two ;  the  ammoniacal  liquors  and  the  gas-tar.  The 
former  consists  of  the  condensed  water,  holding  in  solution 
the  ammonia  produced  from  the  nitrogenous  matters  in  the 
coal ;  the  latter  is  a  complex  substance,  containing  in  its 
lighter  portions  certain  volatile  liquids  as  benzene  and  tolu- 
ene, and  certain  volatile  alkaline  bases  as  aniline  and  chiuo- 
line ;  and  in  its  heavier,  certain  phenols  as  phenol  proper 
(carbolic  acid)  and  cresol,  and  certain  solid  hydrocarbons  as 
naphthalene  and  anthracene. 

CARBON    AND   OXYGEN. 

CARBON  DI-OXIDE.  —  Formula  CO2.  Molecular  mass  43 -89. 
Molecular  volume  2.  Relative  density  21 '94.  The  mass  of 
one  liter  is  1*977  grams  (22  criths). 

31O.  History. — Carbon  di-oxide  was  the  first  gas  distin- 
guished from  air.  It  wras  noticed  as  a  distinct  substance  by 
Paracelsus  in  1520 ;  and  soon  after  Van  Helmont  obtained 
it  from  limestone — whence  he  called  it  chalky  air — and  no- 
ticed its  production  in  the  fermentation  of  sugar  and  in  the 
burning  of  charcoal,  and  its  occurrence  naturally.  Black 
showed  in  1757  that  alkalies  absorbed  it  and  that  its  com- 
pounds effervesced  with  acids.  Lavoisier  in  1775  deter- 
mined its  composition  synthetically  by  burning  carbon  in 
oxygen. 


PREPARATION  OF  CARBON  I) I- OXIDE.  237 

311.  Occurrence. — Carbon  di-oxide  exists  in  the  air  to 
the  extent  of  about  O04  per  cent,  being  produced  by  com- 
bustion, fermentation,  respiration,  etc.     In  volcanic  districts 
it  is  more  abundant,  the  large  quantity  of  it  often  collected  in 
low  places  frequently  proving  fatal  to  life.     Combined  with 
calcium  oxide  or  lime,  it  exists  in  enormous  quantity  in  lime- 
stone. 

312.  Preparation. — Carbon  di-oxide  may  be  prepared 
by  direct  synthesis.     It  is  always  the  product  of  the  com- 
bustion of  carbon  in  air  or  in  oxygen : 

C   +    O2   =   CO, 

It  is  generally  obtained,  however,  by  the  action  of  an  acid 
upon  some  carbonate,  as  that  of  sodium  or  of  calcium : 

CaC08  +  (HN03)2  =  Ca"(N08),  +  H2O  +  CO2 

It  is  produced  in  large  quantities  in  burning  limestone  for 
the  production  of  quicklime  : 

CaCO3  =    CaO    +    CO2 

EXPERIMENTS. — All  carbonates  effervesce  with  acids  from  the  set- 
ting free  of  carbon  di-oxide  gas.  If  some  fragments  of  marble  be 
placed  in  the  test-glass  (Fig.  76),  and  some  hydrochlo- 
ric acid  be  added,  a  brisk  effervescence  will  take  place 
from  the  escape  of  this  gas.  In  order  to  collect  it  the 
experiment  may  be  repeated  in  the  two-necked  bottle 
(Fig.  77),  the  acid  being  poured  in  through  the  funnel 
tube  upon  the  marble,  previously  covered  with,  water. 
The  gas  may  be  collected  over  water  or  by  displace- 
ment, as  it  is  denser  than  air.  Fig  ?6  Efferveg. 

313.  Properties. — Carbon  di-oxide  is  a  col-    Senates  w&h 
orless  gas  with  a  slightly  pungent  odor  and  acid 

taste.  It  is  denser  than  air,  its  specific  gravity  being  1  '524. 
At  the  ordinary  temperature  and  pressure,  water  dissolves  its 
own  volume  of  this  gas.  As  the  pressure  increases,  the  tem- 
perature remaining  the  same,  another  volume  is  absorbed 
for  each  atmosphere  added ;  but  as  the  gas  is  condensed  in 


238 


INORGANIC  CHEMISTRY. 


the  same  ratio,  according  to  Marriotte's  law,  it  follows  that 
the  volume  of  the  gas  dissolved  by  water  is  the  same  at  all 
pressures,  while  the  mass  is  directly  proportional  to  the  press- 
ure. Subjected  to  a  pressure  of  38*5  atmospheres  at  0°, 
it  condenses  to  a  colorless  limpid  liquid,  of  specific  gravity 
0-923  at  0°,  0-868  at  10°,  and  0-782  at  20°.  Its  critical 
temperature  is  30'9°  and  its  critical  pressure  is  73 '6  atmos- 
pheres. Cooled  to  —65°,  the  liquid  solidifies  to  a  transpar- 
ent mass  like  ice.  Since  the  pressure  at  this  temperature 
is  3*5  atmospheres,  liquid  carbon  di-oxide  can  not  exist  at  a 
less  pressure.  Under  atmospheric  pressure  it  becomes  a  gas 

or  a  solid.  When  therefore 
a  fine  stream  of  the  lique- 
fied gas  is  allowed  to  es- 
cape into  the  air,  the  rapid 
evaporation  of  one  portion 
freezes  another,  producing 
a  snow-white,  flocculent 
mass,  which  may  be  formed 
into  balls  like  snow,  and 
which  disappears  with 
great  slowness,  producing 
a  temperature  of  —78°. 
Moistened  with  ether  and  placed  in  the  vacuum  of  an  air- 
pump,  a  temperature  of  —140°  may  be  obtained.  Carbon 
di-oxide  extinguishes  the  combustion  of  burning  bodies 
placed  in  it  and  is  fatal  to  animal  life,  though  less  actively 
than  was  formerly  supposed.  Diluted  largely  with  air  it 
exerts  a  narcotic  action,  and  has  been  proposed  as  an  anaes- 
thetic. Fatal  effects  have  resulted  from  entering  wells,  fer- 
menting vats,  and  other  places  in  which  this  gas  has  accu- 
mulated. Before  going  into  such  a  place,  a  lighted  candle 
should  be  lowered  into  it ;  if  it  is  extinguished,  the  place  is 
unsafe.  This  gas  constitutes  the  so-called  "  choke-damp"  and 
"after-damp"  frequently  found  in  coal-mines. 


Fig.  77.  Preparation  of  Carbon  di-oxidc 


LIQUEFACTION  OF  CARBON  Dl-OXIDE. 


239 


EXPERIMENTS.— Carbon  di-oxide  may  be  condensed  to  a  li(juid  by 
the  apparatus  either  of  Thilorier,  in  which  the  gas,  cooled  below 

30-9°,  is  liquefied  by  its  own  pressure; 

or  of  Natterer,  in  which  the  pressure 

is  produced  mechanically.     Fig.  78 

represents  Bianchi's  modification  of 

Natterer's   condensing   pump.     The 

piston  is  solid  and  is  worked  by  a 

crank   and   fl}--wheel,  as    shown   in 

the  figure.     The  receiver  at  the  top 

of  the  pump-barrel  is  made  of  heavy 

cannon-metal,  and  has  a  tight  valve 

below,  and  a  screw-plug  above,  by 

which  the  liquefied  gas  may  be  drawn 

off.     The  tube  leading  to  the  pump 

serves  to  convey  the  dry  carbon  di- 
oxide; as  the  pump  is  worked,  the 

pressure  in  the  receiver  increases  till 

it  reaches  38-5  atmospheres— the  re- 
ceiver being  surrounded  with  ice — 

when  each  additional  stroke  of  the 

pump  liquefies  the  gas  which  it  forces 

into  it.  -  In  this  way  half  a  kilogram 

of  liquid  carbon  di-oxide  may  be  ob- 
tained in  a  short  time.  The  receiver 

is  then  removed  from  the  pump  and 

inverted,  and  the  gas  allowed  to  escape  into  a  peculiarly  constructed 

cylindrical  box  of  metal, 
which  in  the  course  of  a  few 
seconds  is  filled  with  the  sol- 
id carbon  di-oxide  snow.  On 
moistening  some  of  it  with 
ether  in  a  wooden  tray,  and 
immersing  in  the  mixture 
thermometer  -  bulbs  f  u  1 1  of 
mercury,  bullets  of  frozen 
mercury  are  easily  obtained. 
From  the  ease  with  which 
carbon  di-oxide  gas  can  be 

prepared,  it  is  used  to  illustrate  many  of  the  properties  of  gases.     Its 

density  may  be  shown  by  balancing  carefully  a  large  beaker  or  a  thin 


Fig.  78.  Bianchi's  Pump  for  Con- 
densing Gases. 


Fig.  79. 


3  extinguished  by  Carbon 
di-oxide. 


240 


INORGANIC  CHEMISTRY, 


Fig  80.  Drawing 
the  gas  from  a 
well. 


Fig  81.  Candle 
extinguished 
by  C02. 


pasteboard  box  on  one  of  the  scale-pans  of  a  large  balance,  and  pour- 
ing into  it  a  second  large  beakerful  of  the  gas.  The  scale-pan  will  at 
once  descend.  A  candle  lighted  and  placed  in  the  bottom  of  a  beaker 
is  extinguished  on  pouring  some  of  the  gas  upon  it.  If  a  stand  car- 
rying a  series  of  lighted  candles  be 
placed  in  a  large  jar  (Fig.  79),  and 
carbon  di-oxide  gas  be  introduced 
at  the  bottom,  the  candles  will  be 
successively  extinguished  as  the  gas 
rises  around  them.  The  accumula- 
tion of  this  gas  in  wells,  and  its  re- 
moval therefrom  by  buckets,  may 
be  shown  by  using  a  tall  jar  (Fig. 
80)  to  represent  the  well,  and  a  glass 
bucket  attached  to  a  wire  to  draw 
up  the  gas.  If  a  lighted  candle  be 
near,  the  gas  may  be  poured  from 
the  bucket  upon  the  flame  so  as  to 
put  it  out  (Fig.  81).  This  is  the  only  gas  which  extinguishes  flame 
and  renders  lime-water  milky.  If  a  little  clear  lime-water  be  poured 
into  a  jar  of  the  gas,  it  becomes  at  once  turbid  from  the  production 
of  calcium  carbonate. 

314.  Carbonic  Acid. — Formula  H2CO3.  Molecular  tnafis 
61  85. — Carbonic  acid  is  produced  by  the  solution  of  carbon 
di-oxide  in  water.  It  has  not  been  obtained  free  from  water, 
a»  it  readily  decomposes  into  water  and  carbon  di-oxide  again 
on  slightly  raising  the  temperature.  The  solution  in  water  is  a 
distinctly  acid  liquid  having  the  pungent  odor  and  agreeable 
acid  taste  so  well  known  in  the  so-called  soda-water,  which  is 
made  simply  by  condensing  carbon  di-oxide  gas  into  water. 

The  salts  of  carbonic  acid  are  called  carbonates.  •  Both 
ortho- carbonates  and  meta- carbonates,  having  respectively 
the  general  formulas  M'4CO4  and  M'2CO.,,  are  known. 

The  simplest  test  for  a  carbonate  is  the  effervescence  which 
results  when  it  is  treated  with  an  acid.  The  escaping  gas 
may  be  passed  through  lime-water,  which  is  rendered  milky 
by  carbon  di-oxide,  and  becomes  clear  again  on  the  addition 
of  a  dilute  acid. 


PREPARATION  OF  CARBON  MONOXIDE.  241 

CARBON  MONOXIDE  OR  CARBON  YL.  —  Formula  CO.  Molecular 
mass  27*93.  Molecular  volume  2.  Relative  density  13  '96. 
The  mass  of  one  liter  is  1'25  grains  (14  criths). 

315.  History.  —  Carbon  monoxide  was  discovered  by  Las- 
sone  in  1776,  and  also  by  Priestley  in  1783.    Its  true  nature 
was  determined  by  Woodhouse  in  1800. 

316.  Preparation.  —  Carbon  monoxide  may  be  prepared 
(1)  by  the  incomplete  combustion  of  carbon,  as  when  char- 
coal and  blacksmith's  scales  —  ferroso-ferric  oxide  —  are  heated 


Fe30,  +  C.  =  Fes  +   (CO), 

(2)  by  the  abstraction  of  oxygen  from  carbon  dioxide,  as 
when  this  gas  is  passed  over  heated  charcoal  : 

CO,   +    C   =    (CO), 

(3)  by  heating  oxalic  acid  with  strong  sulphuric  acid  : 

H,C2O4    =    H2O    +    CO,     +     CO 

Oxalic  acid.  Water.  Carbon  Carbon 

di-oxide.         monoxide. 

EXPERIMENT.—  For  preparing  carbon  monoxide  from  oxalic  acid, 
such  an  apparatus  as  is  shown   in  Fig.  82  is  required.     The  oxalic 


Fig.  82.  Preparation  of  Carbon  monoxide. 

acid  is  placed  in  the  flask,  enough  sulphuric  acid  is  added  to  cover 
it.  and  the  whole  is  heated  in  a  cup  of  sand  over  the  gas-flame.  The 
gases  as  evolved  pass  into  a  washing-bottle  containing  a  solution  of 


242  ixomtAyic  CHEMISTRY. 

potassium  hydroxide,  in  bubbling  through  which  the  carbon  di-oxide 
is  absorbed;  the  carbon  monoxide  thus  purified  maybe  collected  over 
water. 

317.  Properties. —  Carbon  monoxide  is  a  colorless  gas 
having  a  peculiar  suffocating  odor.     It  is  condensable  to  a 
liquid,  the  critical  temperature  required  being  — 139'5°  and 
the  critical  pressure  35'5  atmospheres.     Its  temperature  un- 
der atmospheric  pressure  is  —190°  and  in  vacuo  —211°.     At 
this  point  it  solidifies,  yielding  a  clear  mass  like  ice  if  the 
freezing  be  slow,  but  a  snowy  mass  if  it  be  rapid.     (Olszew- 
ski.)     It  requires  40  times  its  volume  of  water  for  solution. 
Its  specific  gravity  is  0'969.     It  is  readily  combustible,  burn- 
ing in  the  air  or  in  oxygen  with  the  characteristic  lambent 
blue  flame  often  seen  playing  over  a  freshly  fed  anthracite 
fire.     It  unites  directly  with  chlorine  in  sunlight,  forming 
carbonyl  chloride,  or  phosgene  gas.    It  is  totally  irrespirable, 
being  an  active  narcotic  poison,  one  per  cent  in  the  air  prov- 
ing fatal.     Its  presence  in  "  water-gas,"  produced  by  passing 
steam  over  red-hot  charcoal,  has  been  the  occasion  of  legis- 
lative interference  ;  the  amount  of  carbon  monoxide  permis- 
sible in  a  gas  used  for  illumination  being  now  fixed  by  law 
in  several  of  the   States.     The  ready  passage  of  this   gas 
through  heated  cast  iron,  and  its   consequent  presence  in 
apartments  heated  by  stoves  or  furnaces  of  this  metal,  has 
been  assumed  as  the  cause  of  serious  disease  in  many  in- 
stances.  With  sufficient  ventilation,  however,  no  danger  from 
this  cause  need  be  apprehended. 

COMBUSTION.  ;  • 

318.  Definition. — In  the  wide  sense  of  the  term,  com- 
bustion is  an  energetic  chemical  action,  attended  with  light 
and  heat.*    It  is  commonly  restricted,  however,  to  the  direct 
union  of  a  substance  with  oxygen.     Two  substances  at  least 
are  concerned  in  every  combustion  :  the  combustible,  or  the 
body  which  burns ;  and  the  supporter  of  combustion,  or 


COMBUSTION  AND  COMBUSTIBLES.  243 

the  gas  in  which  the  combustion  takes  place.     Commonly 
we  call  hydrogen  a  combustible  body,  and  air  a  supporter 
of  combustion  ;    but  if  the  atmosphere  were 
hydrogen,  then  the  oxygen  would  burn  in  it 
and  would  be  the  combustible  body. 

EXPERIMENT. — It  is  commonly  said  that  coal-gas 
burns  in  the  air;  but  if  ajar  be  filled  with  coal-gas, 
and  a  combustion-spoon  containing  melted  potas- 
sium chlorate  be  introduced  into  it  (Fig.  83),  the 
oxygen  given  off  will  burn  in  the  coal-gas,  the  latter 
being  now  the  supporter. 

319.  Combustibles. — The  substances 
which  are  burned  as  combustibles  are  very    burning 
numerous.    Illuminating-gas  has  already  been 
mentioned.     Of  liquids,  the  vegetable  oils  known  as  rape, 
olive,  and  turpentine,  the  animal  oils  called  sperm  and  lard, 
and  the  mineral  oils  derived  from  petroleum,  may  be  men- 
tioned.    Of  solids  from  the  vegetable  kingdom,  wood  and 
bayberry   wax ;    from   the   animal,  tallow   and  its  product, 
stearin ;  and  from  the  mineral,  paraffin  and  the  various  sorts 
of  coal,  are  examples.    These  substances,  though  so  different 
in  character  and  origin,  all  agree  in  the  fact  that  they  con- 
tain carbon  and  hydrogen.     Some  contain  oxygen  in  addi- 
tion. 

320.  Combustion  itself. — Bodies  are  burned  either  for 
purposes  of  warmth  or  of  illumination.    The  temperature  at 
which  bodies  take  fire  in  the  air  differs  widely ;  phosphorus, 
for  example,  inflames  at  50°;  sulphur  at  260°;  hydrogen  at 
500°;  while  coal-gas  requires  a  temperature  of  1000°,  and 
nitrogen   one   of  5400°.      The   amount  of  heat   and  light 
evolved  are  proportional  to  the  rapidity  of  the  combustion. 
In   the  decay  of  wood  there  is  a  true  burning,  called  by 
Liebig  eremacausis ;   but  though  the  heat  produced -is  the 
same  in  slow  as  in  rapid  combustion,  the  rise  of  temperature 
in  the  former  case  is  small,     Phosphorus  exposed  to  the  air 


244 


INOEGA  NIC  CHE  MIS  TE  Y. 


becomes  luminous  and  slowly  oxidizes ;  but  the  temperature 
never  rises  very  high.  When  heated  very  hot,  however,  bod- 
ies undergo  a  rapid  combustion  and  evolve  their  maximum 
temperature.  When  the  matter  burning  is  gaseous,  then 
the  phenomenon  of  flame  appears.  The  char- 
acter of  flame  may  be  very  well  studied  in  that 
of  an  ordinary  candle  (Fig.  84).  The  solid  mat- 
ter melted  by  the  heat  is  drawn  up  in  the  wick 
as  a  liquid,  and  is  converted  in  the  flame  into 
gas.  In  the  center  of  the  flame  then  there  is 
a  dark  cone  of  inflammable  gas.  Surrounding 
this  there  is  the  luminous  envelop,  where  con- 
densed hydrocarbons  are  undergoing  combus- 
tion. And  outside  still  is  the  portion  of  the 
flame  called  the  mantle,  faintly  blue  in  color, 
composed,  it  is  said,  of  burning  hydrogen,  and 
cup-shaped  at  its  lower  portion. 

EXPERIMENTS. — By  means  of  a  glass  tube  the  com- 
bustible gas  in  the  center  of  a  candle-flame  may  be 
easily  led  off  and  burned.     Moreover,  burning  phos- 
Fig.  84  Caudle-    phorus  is  extinguished  when  placed  in  the  center  of  a 
large  alcohol-flame,  thus  showing  the  absence  of  air 
there.     A  porcelain  plate  held  in  the  luminous  cone  will  have  the 
condensed  hydrocarbons  deposited  upon  it;  i.  e.,  will  be  smoked. 

In  order  to  burn  this  gaseous  matter  in 
the  center  of  the  flame,  Argand  proposed 
the  burner  now  known 
by  his  name.  In  this 
burner  air  is  admitted 
into  this  gaseous  space 
by  making  the  flame 
ring-shaped.  Moreover, 
by  using  a  chimney  to 

Fig.  85.  Argand  burner    produce     a    draft>    great 

brilliancy  and  steadiness  are  given  to  the  flame.    For  heating 


Fig.  86.  Bunsen's 
burner. 


COMBUSTIOX.  245 

purposes,  the  best  burner  is  Bunsen's  burner  (Fig.  86).    The 

<rus,  issuing  from  a  small  central  jet,  is  thoroughly  mixed 

with  air  entering  by  the  lateral  openings, 

before  it  burns  at  the  top  of  the  tube.    By 

this  dilution,  which  may  be  made  equally 

well  with  nitrogen  or  carbon  di-oxide,  the 

density  of  the  gas  is  so  reduced  that  the 

flame  is  non-luminous,  and  no  smoke  is 

deposited  on  bodies  held  in  it. 

Flame,  if  cooled  below  a  certain  point, 
is  extinguished  ;  hence  no  flame  can  be 
propagated  through  a  cold,  fine  metal  tube. 
This  was  Davy's  discovery,  which  gave 
rise  to  the  safety-lamp. 

EXPERIMENTS. — Wire-gauze  is  simply  a  col- 
lection of  small,  short  tubes.  If  a  piece  of  such 
gauze  be  pressed  upon  a  gas-flame,-  the  flame 
will  not  pass  through  it,  but  will  be  depressed 
by  it  as  if  it  were  a  solid  plate.  If  held  two 
inches  above  the  jet,  the  gas  may  be  lighted 
above  the  gauze,  but  the  flame  will  not  pass 
through  to  the  jet.  With  two  pieces  of  gauze 
the  gas  may  be  made  to  burn  between  them,  but 

neither  above  the  upper  nor  below  the  lower;  or  above  and  below, 
but  not  between  them. 

The  miner's  safety-lamp  is  represented  in  section  in  Fig. 
87.  It  consists  of  a  metallic  lamp,  the  wick  of  which  is  sur- 
rounded with  wire-gauze,  inclosed  in  a  frame,  by  which  the 
whole  may  be  suspended.  The  explosive  mixture  of  air  with 
the  gases  of  the  mine  can  enter  the  gauze  and  burn  within 
it;  but  the  flame  can  not  pass  outward  through  the  gauze, 
as  it  is  thereby  cooled  and  extinguished.  Hence,  with  such 
-a  lamp  an  explosion  of  these  gases  can  not  take  place. 

321.  Products  of  Combustion. — The  products  of  com- 
bustion are  of  two  sorts:  1st,  the  physical  products,  the 
heat  and  light  for  which  the  combustion  is  generally  pro- 

17 


246  INORGANIC  CHEMISTRY. 

duced.  2d,  the  chemical  products,  which  are  to  be  con- 
veyed away.  The  heat  of  combustion  is  measured  in  heat- 
units;  a  heat-unit  being  the  quantity  of  heat  required  to 
raise  one  gram  of  water  from  0°  to  1°.  Thus  the  heat  of 
combustion  of  hydrogen  in  oxygen  is  34,180  units,  and  that 
of  carbon  8,080  units ;  i.  e.,  one  gram  of  hydrogen  or  of  car- 
bon in  burning  in  oxygen  would  heat  34,180  or  8,080  grams 
of  water  from  0°  to  1°.  Knowing  the  quantity  of  carbon 
and  hydrogen  in  a  given  fuel,  therefore,  it  is  easy  to  calcu- 
late its  value  for  heating  purposes. 

The  light  given  by  an  illuminating  agent  is  measured  by 
comparison  with  that  of  a  standard  candle,  as  mentioned 
under  coal-gas.  The  instrument  used  for  this  comparison  is 
called  a  photometer. 

The  chemical  products  of  combustion,  since  the  combus- 
tibles are  composed  of  carbon  and  hydrogen,  are  obviously 
carbon  di-oxide  and  hydrogen  oxide  or  water. 

EXPERIMENTS.  —  That  water  is  produced  in  combustion  may  be 
shown  by  holding  a  cold  dry  bell-glass  over  a  candle-flame;  it  will 
be  at  once  bedewed  with  moisture.  If  now  a  little  clear  lime-water 
be  shaken  in  the  jar,  it  will  become  milky,  thus  proving  the  presence 
of  carbon  di-oxide.  The  same  is  true  of  respiration;  a  full  breath 
blown  through  a  glass  tube  into  lime-water  will  make  it  entirely 
white.  Air  that  has  been  twice  respired  will  also  extinguish  a  candle. 

322.  Ventilation.— To  carry  off  these  effete  products, 
an  efficient  ventilation  is  necessary.  This  is  generally  se- 
cured by  a  draft  produced  by  heat,  carrying  all  the  foul  air 
into  a  ventilating  shaft  and  thence  into  the  outer  air.  Air 
is  too  impure  to  breathe  if  it  contains  0-10  per  cent  of  car- 
bon di-oxide ;  but  numerous  other  organic  and  inorganic  im- 
purities are  produced  by  respiration  and  by  combustion  in 
our  houses  which  are  quite  as  injurious  to  health,  and  which 
must  also  be  removed. 

EXPERIMENTS. — The  principles  of  ventilation  may  be  illustrated 
by  the  following  experiments:  If  a  tall  bell-glass,  closed  at  top,  be 


PSINCIPL A'.v  or  \ 'KSTILA T-ION. 


247 


placed  over  a  stand  on  which  are  three  lighted  caudles  at  different 
heights  (Fig.  88),  the  heated  carbon  di-oxide  will  accumulate  in  the 
upper  part  of  the  bell,  and  gradually  extinguish  the  tapers  from  above 
downward.  By  removing  the  stopper  and  rais- 
ing the  jar  just  before' the  last 
flame  expires,  the  air  is  re- 
newed and  the  taper  will  be 
revived. 

•  If  a  wide  glass  tube  be  fixed 
in  the  neck  of  the  bell,  as 
shown  in  Fig.  89,  and  this  be 
placed  over  a  stand  carrying 
two  tapers,  both  will  be  ex- 
tinguished as  before.  But  if 

a  small  space  be  left  between    Fig.  88.  Accumulation 
tf?n  wUha  Draft     the  bell  and  the  plate,  the  up-       °ff  &$£»«  part 

per  taper  only  will  go  out, 

while  the  lower  one  will  be  supplied  with  air  from  below,  its  carbon 
di-oxide  and  water  escaping  through  the  tube. 

Again,  if  two  large  tubes,  one  within  the  other,  be  fixed  in  the 
neck  of  a  bell-glass  (Fig.  90),  and  the  whole  be  placed  over  a  candle- 
flame,  the  heated  and  effete  products  of  combustion  escape  up  the 
center  tube,  while  fresh  air  enters  by  the  an- 
nular space  between  the  two,  and  the  candle 
burns  actively. 

Mines  are  usually  ventilated  by  means  of 
two  shafts,  called  the  upcast  and  the  down- 

I 


Fig  90.  Double-draft  Ap- 
paratus. 


Fig.  91.  Upcast  and  Downcast 
Shafts. 


cast  shafts,  respectively.  Their  action  may  be  represented  by  Fig.  91. 
A  square  box  has  at  each  end  a  chimney,  in  one  of  which  a  candle  is 
kept  burning.  The  air  heated  by  the  combustion  rises,  while  fresh 


248  INORGANIC  CHEMISTRY. 

air  descends  in  the  opposite  chimney  to  supply  its  place.    Practically, 
a  coal  fire  is  kept  burning  at  the  base  of  the  upcast  shaft,  and  by 
suitably,  arranging  doors  in  the  different  parts  of 
the  mine,  the  whole  may  be  thoroughly  ventilated. 
If  but  one  shaft  is  possible,  then  an  arrangement 
illustrated  by  Fig.  92  is  generally  employed.     A 
candle  placed  in  a  small  bell-glass  surmounted  by 
a  wide  tube  will  be  extinguished.     But  if  a  piece 
of  tin-plate  be  inserted  in  the  tube,  the  foul  air  will- 
pass  out  on  one  side  and  fresh  air  will  enter  on 
the  other,  and  the  candle  will  continue  to  burn.    It 
was  the  taking  fire  of  such  a  partition,  and  the 
consequent  stoppage  of  ventilation,  which  caused 
the  terrible  disaster  at  the  Avondale  colliery  a  few 
years  ago;  the  choke-damp  as  well  as  the  fire-damp    Fig. 92.  Single  shaft 
accumulating  in  the  mine  in  co/isequence,  and  pro- 
ducing fatal  results. 

CARBON    AND    SULPHUR. 

CARBON  DI-SULPHIDE. — Formula  CS.r  Molecular  mass  75 -93. 
Molecular  volume  2.  Relative  density  of  vapor  37 '96.  The 
mass  of  one  liter  of  carbon  di-sulphide  vapor  'is  3*40  grams 
(38  criilis). 

323.  History  and  Preparation.  —  Carbon   disulphide 
was  discovered  by  Lampadius  in  1796.     It  is  always  pre- 
pared synthetically,  by  passing  the  vapor  of  sulphur  over 
charcoal  heated  to  redness  : 

.    C,   +    (S,),   =    (CS2), 

By  agitating  with  lead  hydrate   or  mercuric  chloride,  and 
re-distilling  from  milk  of  lime,  it  is  obtained  pure. 

324.  Properties.  —  Carbon  di  -  sulphide  is  a  colorless, 
strongly  refracting  liquid,  having,  when  perfectly  pure,  an 
agreeable  ethereal  odor,  like  chloroform.     Its  specific  grav- 
ity is  1-27.     It  solidifies  at  —116°,  melts  again  at  —110°, 
and  boils  at  46°,  yielding  a  dense  vapor.     It  is  very  volatile, 
evaporating  rapidly  in  the  air,  with  the  production  of  great 
cold.    It  is  not  soluble  in  water,     Its  vapor  is  readily  inflam- 


249 

mable,  taking  fire  in  the  air  even  at  150°,  and  burning  with 
a  blue  flame,  producing  carbon  and  sulphur  di-oxides.  The 
brilliancy  of  its  combustion  with  nitrogen  di-oxide  has  been 
already  mentioned. 

Carbon  di- sulphide  unites  directly  with  alkali -sulphides 
and  sulphydrates,  producing  sulpho-carbonates  M2CSS,  anal- 
ogous to  carbonates  M,CO3.  By  decomposing  ammonium 
sulpho  -  carbonate  with  hydrochloric  acid,  sulpho  -  carbonic 
acid  H2CS3  is  obtained  as  a  reddish-brown  oily  liquid  : 

(NHJ2CS3  •  +  (HC1),  =  (NH4C1)2  +  H,Cfe3 

325.  Uses.  —  Carbon  di-sulphide  is  used  in  the  arts  to 
dissolve  phosphorus,  iodine,  and  sulphur ;  the  latter  particu- 
larly in  vulcanizing  india-rubber.     It  is  largely  used  also  as 
a   solvent  for   resins  and   bitumens ;   and  of  late  years  has 
been  prepared  on  an  immense  scale  for  the  extraction  of  the 
various  fatty  and  essential  oils. 

CARBON    AND    NITROGEN. 

CYANOGEN.  —  Formula  C.,N2.  Symbol  Cy.  Molecular  max* 
51-96.  Molecular  volume  2.  Relative  density  -25*98.  The 
mass  of  one  liter  is  2%32  grams  (26  criths). 

326.  History. — Cyanogen  was  discovered  by  Gay-Lus- 
sac  in  1815.     It  was  the  first  compound  radical  isolated,  and 
its  discovery  marks  an  era  in  the  science  of  chemistry.     Its 
name  is  from  xudvsoz,  dark  blue,  it  being  a  constituent  of  the 
well-known  pigment,  prussian-blue. 

327.  Preparation.  —  Cyanogen  is  usually  prepared  by 
heating  the  cyanide  of  gold,  silver,  or  mercury: 

HK"Cy,   =    Hg    +    Cy, 

EXPERIMENT. — Instead  of  using  the  somewhat  rare  mercuric  cya- 
nide, a  mixture  of  two  parts  of  thorough^  dried  potassium  ferro- 
cyanide  and  three  parts  mercuric  chloride  may  be  advantageously 
substituted.  The  mixture  is  placed  in  a  flask  of  hard  glass  (Fig.  93), 
upon  a  sand-bath,  and  heated  intensely  by  means  of  the  double-draft 


250  INORUAMC  CIIKMfxrHY. 

gas-burner.     The  gas  as  it  is  evolved  may  be  collected  by  displace- 
ment, the  pungent  odor  indicating  when  the  jar  is  full. 

328.  Properties. — Cyanogen  is  a  colorless  gas,  with  a 
penetrating,  pungent  odor,  resembling  that  of  peach-blos- 
soms. Its  specific  gravity  is  1'806.  Cooled  to  — 2O7,  or 
subjected  to  a  pressure  of  four  and  a  half  atmospheres  at 
15°,  it  condenses  to  a  colorless,  highly  refractive  liquid,  of 

specific  gravity  0'866, 
which  freezes  at  —34° 
to  a  transparent,  ice- 
like  solid.  Its  critical 
pressure  is  61 '7  atmos- 
pheres and  critical  tem- 
perature 124°.  Cyan- 
ogen gas  is  soluble  in 
one  fourth  of  its  vol- 
ume of  water  and  in 
one  twentieth  of  its  vol- 
ume of  alcohol.  It 
takes  fire  readily  in 

the   air,   burning    with 
Fig.  93.  Preparation  of  Cyanogen. 

a  characteristic  purple- 
red  flame,  producing  carbon  di-oxide  and  nitrogen. 

Free  or  molecular  cyanogen  is  composed  of  two  atoms  of 
the  cyanogen  radical,  Cy,  being  analogous  to  C1.2.  Moreover, 
atomic  cyanogen  acts  precisely  like  an  elemental  monad, 
forming  compounds  corresponding  to  the  chlorides,  thus : 

Potassium  chloride  KC1.  Potassium  cyanide  KCy. 

Hydrochloric  acid  HC1.  Hydrocyanic  acid    HCy. 

Hypochlorous  acid  HC1O.  Cyanic  acid  HCyO. 


The  thermo-chemical  relations  of  carbon  are  noteworthy. 
Berthelot  has  shown  that  in  the  form  of  diamond  one  gram 
of  carbon  in  uniting  with  oxygen  evolves  7,859  heat-units, 
one  gram  of  graphite  7,901,  and  one  gram  of  charcoal  8,137 


SJLfCON.  251 

heat-units.  The  heat  of  formation  of  methane  CH4  from 
amorphous  carbon  and  hydrogen  is  21,750  heat-units;  of 
ethylene  —2,700,  and  of  acetylene  —48,300  heat-units.  This 
absorption  of  energy  results  from  the  fact  that  to  separate 
the  carbon  atoms  in  the  molecule  and  to  convert  the  solid 
carbon  into  gas,  work  must  be  done  upon  it ;  calculation  show- 
ing that  12  grams  of  amorphous  carbon  thus  separated  ab- 
sorb 38,300  heat-units.  The  readiness  with  which  acetylene 
and  ethylene  unite  directly  with  hydrogen  is  thus*  apparent. 
To  form  CC14  from  chlorine  and  amorphous  carbon,  21,030 
heat-units  must  be  set  free ;  so  that,  to  judge  by  this  standard, 
the  attraction  of  carbon  for  hydrogen  is  practically  the  same 
as  that  for  chlorine.  The  heat  of  formation  of  carbon  mon- 
oxide CO  is  28,500  units ;  that  of  carbon  di-oxide  CO,,  also 
from  amorphous  carbon  and  oxygen,  is  96,900  units.  Hence 
when  CO  burns  to  CO2,  68,400  heat-units  are  evolved.  The 
heat  of  formation  of  CS2  is  negative  and  is  —12,600  units. 
The  formation  of  free  cyanogen  C2N2  is  also  endothermic, 
the  absorption  of  heat  being  — 65,700  units. 

§  2.   SILICON. 

Symbol  Si.  Atomic  mass  28.  Valence  IV.  Relative  density 
28  (?).  Molecular  mass  56  (?).  Molecular  volume  2.  The 
mass  of  one  liter  of  silicon-vapor  is  2  '5  grams  (28  critJis)  (?). 

329.  History  and  Occurrence. — Silicon  was  first  ob- 
tained pure  by  Berzelius  in  1823.     It  does  not  occur  free 
in  nature,  but  exists  abundantly  in  combination  with  oxy- 
gen, forming  the  well-known  substance,  quartz.     Combined 
with  oxygen,  and  also  with  potassium,  aluminum,  and  other 
metals,  it  constitutes  a  large  portion  of  the  rocks  which  make 
up  the  solid  crust  of  the  earth. 

330.  Preparation.  —  Silicon  may  be  prepared  by  the 
action  of  sodium  upon  potassium  fluo-silicate : 

K2SiF6  +  Na4  =  (KF)2  +  (NaF)4  +  Si 


252  IXOIH'.AXIC  CIIEM1STHY. 

331.  Properties. — Silicon  as  thus  obtained  is  an  amor- 
phous, nut-brown,  lusterless  powder,  which  may  be  crystal- 
lized by  solution  in  melted  zinc,  in  long  needles  made  up 
of  adhering  regular  octahedrons;   or  in  melted  aluminum, 
in  flat  octahedral  plates.     In  this  form  it  is  a  dark  iron-gray 
solid,  with  a  metallic  luster  and  a  specific  gravity  of  2 '49. 
It  is  hard  enough  to  scratch  glass,  and  melts  at  a  tempera- 
ture above  the  melting  point  of  iron.     Heated  in  the  air, 
the  amorphous  silicon  takes  fire  and  burns,  producing  silicic 
oxide. 

SILICON    AND    HYDROGEN. 

HYDROGEN  SILICIDE. — Formula  H48i.     Molecular  mans  32. 

332.  History  and  Preparation. — Hydrogen   filicide 
was  first  observed  by  Wohler  and  Buff  in  1857;   but  it  was 
first  obtained  pure  in  1867  by  Friedel  and  Ladenburg. 

It  may  be  obtained,  mixed  with  hydrogen,  by  the  electro- 
lysis of  a  solution  of  sodium  chloride,  a  plate  of  aluminum 
containing  silicon  being  made  the  positive  electrode.  A 
better  process  is  to  decompose  magnesium  silicide  by  hydro- 
chloric acid : 

Mg.2Si  -f  (HC1)4  =  (MgCl.2)2  +  H4Si 

It  is  obtained  perfectly  pure  by  the  action  of  sodium  upon 
tri-ethyl  silico-formate. 

EXPERIMENT.  —  For  preparing 
magnesium  silicide,  40  parts  fused 
magnesium  chloride,  35  parts  dried 
sodium  fluo-silicate,  10  parts  fused 
sodium  chloride,  and  20  parts  of 
sodium  cut  into  small  pieces,  are 
well  mixed  together  and  thrown 
into  a  red-hot  hessian  crucible, 
which  is  then  covered  and  heated  Fig.  94>  Preparation  of  Hydrogen 
until  the  sodium  ceases  to  burn.  Silicide. 

When  cold,  a  dark  layer  of  the  impure  silicide  will  be  found  at  the 
bottom.     It  is  detached  and  preserved  in  a  tight  bottle. 


iKX  SI  LIC-I  !)/<;.  253 

To  obtain  hydrogen  silieitle,  the  coarsely  pulverized  slag  thus  made 
is  placed  in  a  wide-mouthed  bottle  (Fig.  04),  through  the  cork  of 
which  passes  a  funnel  tube  for  adding  the  acid,  and  a  wide  delivery 
tube  for  the  escape  of  the  gas.  The  bottle  is  then  filled  with  cold 
water  —  recently  boiled  to  expel  the  air  —  and  placed  by  the  water- 
cistern  as  shown  in  the  figure.  Upon  pouring  concentrated  hydro- 
chloric acid  down  the  funnel  tube  — taking  especial  care  that  it  carries 
in  no  air-bubbles — hydrogen  silicide  gas  is  evolved  and  may  be  col- 
lected for  use. 

333.  Properties. — Hydrogen  silicide  is  a  colorless  gas, 
which,  when  mixed  with  hydrogen,  is  spontaneously  inflam- 
mable in  the  air,  yielding  white  clouds  of  silicic  oxide.     At 
the  temperature  of  — 5°,  a  pressure  of  70  atmospheres  con- 
denses it  to  a  liquid.     Burned  from  a  jet,  it  gives  a  brilliant 
white  flame,  wrhich  deposits  a  brown  layer  of  silicon  upon  a 
piece  of  porcelain  held  in  it.     When  the  tube  conveying  the 
<zas   LS  heated,  a  mirror-like  deposit  of  silicon  takes  place 
within  it.     Hydrogen  silicide  is  not  soluble  in  water.    Passed 
into  cupric  sulphate  or  silver  nitrate,  it  throws  down  cupric 
and  silver  silicides.     It  is  decomposed  by  potassium  hydrox- 
ide, one  volume  of  the  gas  yielding  four  volumes  of  hydro- 

SiH4  +  (HKO)4  =  K4Si04  +  H8 

One  half  of  this  hydrogen  comes  from  the  silicide ;  each 
molecule  must  therefore  contain  two  molecules  of  hydrogen, 
or  four  atoms. 

SILICON    AND    OXYGEN. 

SILICIC  OXIDE. — Formula  SiO2.     Molecular  mass  59*92. 

334.  Occurrence. — Silicic  oxide,  or  silica,  occurs  abun- 
dantly in  nature  in  the  pure  and  crystallized  form  known 
as  quartz  or  rock-crystal ;   and  more  or  less  deeply  colored 
in  the  minerals  called  amethyst,  jasper,  agate,  chalcedony, 
and  carnelian.     A  beautiful  and  probably  polymeric  form  is 
known  as  opal.     As  sandstone  it  forms  a  rock-nmterial  in 
geology.     Its  combinations  with  metallic  oxides,  called  sili- 


254  lyoiidAXIC  CHEMISTRY. 


cates,  form  by  far  the  most  numerous  class  of  mineral  sub- 
stances. Silicic  oxide  also  occurs  dissolved  in  many  natural 
waters,  particularly  those  of  thermal  springs  ;  it  stiffens  the 
stems  of  the  cereal  grains,  and  has  been  also  found  in  animal 
tissues. 

335.  Preparation.  —  Silicic  oxide  may  be  prepared  either 
by  the  oxidation  of  silicon,  as  when  it  burns  in  the  air,  or 
by  the  dehydration  of  silicic  acid  : 

H,SiO3  --  H,0  =  SiO2 

336.  Properties.  —  Silicic  oxide,  as  usually  obtained,  is 
a  white  amorphous  powder,  though  in  nature  it  occurs  often 
in  the  form  of  hexagonal  prisms,  crowned  by  six- 

sided  pyramids  (Fig.  95).  It  has  a  specific  grav- 
ity of  2  '60,  is  so  hard  as  readily  to  scratch  glass, 
and  is  fusible  only  by  the  oxyhydrogeu  flame.  It 
is  but  slightly  soluble  in  water,  and  is  unattacked 
by  acids,  except  the  hydrofluoric.  Fused  with 
salts  of  the  alkali-metals,  it  combines  with  the 
basic  oxide,  forming  a  silicate,  and  sets  the  nega- 
tive or  acid  oxide  free. 

337.  Silicic  Acid.  —  Ortiw  H4Si  lv  O4.     Meta 
H2SilvO3.     Ortho-silicic  acid  may  be  prepared  by 

the  action  of  water  on  silicon  fluoride,  or  by  decomposing  a 
solution  of  an  alkaline  silicate  by  an  acid.  It  is  obtained  as 
a  gelatinous  precipitate,  losing  water  when  dried,  and  pro- 
ducing meta-silicic  acid.  By  dialysing  a  solution  of  an  alka- 
line silicate  in  hydrochloric  acid,  the  acid  passes  through  the 
membrane,  and  there  is  left  in  the  dialyser  an  aqueous  solu- 
tion of  silicic  acid,  which  may  be  concentrated  by  boiling  in 
a  flask  until  it  contains  37  per  cent.  It  is  a  tasteless,  lim- 
pid liquid,  is  slightly  acid,  and  becomes  a  jelly  on  standing. 
On  evaporation  it  leaves  meta-silicic  acid.  A  third  silicic 
hydrate,  called  para  -silicic  or  di-  silicic  acid,  H6Si2O7,  is 
known. 


ttELATio\s  or  TIIK  r.////;av  aitour.  255 

The  silicates  are  classified  by  Dana  as  uni-silicates,  M'4SiO4, 
corresponding  to  ortho-silicates,  and  bi-silicates,  M'2  SiO,,  cor- 
responding to  meta-silicates.  Some  of  the  intermediate  vari- 
eties, such  as  wernerite  [Na,  Ca,  Al]",  Si2O7,  are  di-  or  para- 
silicates ;  others,  as  lepidolite  [K,  Li,  Mn,  Al]"4Si3O10,  and 
labradorite  [Ca,  Na,  Al]"4Si3O10,  are  derived  from  tri-silicic 
acid,  H8Si3O10.  Besides  these  there  is  a  third  class  of  sili- 
cates— Dana's  sub-silicates — which  are  meta  -  aluminic  sili- 
cates, derived  from  meta-aluminic  base  H4A12O5 — by  replac- 
ing the  H4  by  Silv.  In  this  way  the  mineral  cyanite,  SiAl.2O5, 
is  produced.  Potassium  and  sodium  meta-silicates  are  solu- 
ble in  water,  and  their  solutions  are  used  in  the  arts  under 
the  name  of  soluble  glass.  Potassio-lead  silicate  is  known  in 
commerce  as  flint  glass,  and  sodio-calcium  silicate  as  window 
glass.  Crown  glass,  used  for  optical  purposes,  and  Bohemian 
glass,  of  which  chemical  vessels  are  made,  are  potassio-cal- 
cium  silicates.  Plate  glass  contains  potassium,  sodium,  and 
calcium  as  its  basic  constituents. 

RELATIONS  OF  THE  CARBON  GROUP. 

338.  Carbon,  silicon,  and  titanium,  as  well  as  zirco- 
nium, cerium,  and  thorium,  are  closely  related  to  each  other 
in  the  gradation  of  their  physical  properties  as  well  as  in  the 
similarity  of  their  chemical  compounds.  Their  tetrad  char- 
acter is  well  marked,  since  they  form  tetra-chlorides,  di-ox- 
ides,  and  di-sulphides,  and  since  carbon  and  silicon  form  also 
tetra-hydrides.  The  elements  of  this  group  are  also  capable 
of  entering  into  combination  as  double  atoms,  with  an  equi- 
valence of  six,  forming  the  chloride  of  carbon  C2C16  and  the 
oxide  of  titanium  Ti.2O3,  for  example.  Finally  they  all  form 
normal  ortho-hydrates,  which  are  tetra-basic  or  acidic,  and 
derived  meta-hydrates,  which  are  di-basic  or  acidic. 


IS  ORGANIC  CHEMISTRY. 


EXERCISES. 
$1* 

1.  Mention  the  forms  in  which  carbon  occurs  in  nature. 

2.  How  are  they  proved  to  be  chemically  identical? 

3.  One  kilogram  of  carbon  in  burning  will  evaporate  how  much 
water? 

4.  How  is  methane  produced  naturally?    How  hiade  artificially? 

5.  What  volume  of  methane  from  a  kilogram  of  sodium  acetate? 

6.  One  gram  of  alcohol  yields  what  volume  of  ethyk'iie? 

7.  A  cubic  meter  of  ethylene  contains  what  volume  of  H? 

8.  For  what  reason  is  ethylene  written  C2H4  and  not  CH.,? 

9.  What  volume  of  O  is  required  to  burn  250  grams  of  ethylene? 

10.  How  is  acetylene  prepared?      What  are  its  properties? 

11.  Describe  the  process  for  making  coal-gas. 

12.  One  kilogram  of  C  in  burning  gives  what  mass  of  CO.,? 

13.  What  mass  of  KC1O3  will  completely  burn  5  grams  of  C? 

14.  What  volume  of  air  is  required  to  burn  one  liter  of  marsh-gas. 
of  ethylene,  and  of  acetylene?     What  volume  of  CO.,  is  produced  in 
each  case? 

15.  What  volume  of  carbon  di-oxide  will  be  produced  by  burning 
a  kilogram  of  cannel  coal,  85-81  per  cent  of  which  is  carbon? 

16.  One  cubic  centimeter  of  marble  (specific  gravity  2-7)  contains 
what  volume  of  CO2? 

17.  How  many  kilograms  of  carbon  in  1,000  kilograms  of  chalk? 

18.  What  volume  of  CO2  must  be  passed  over  charcoal  to  yield  a 
liter  of  CO?     What  is  the  increase  in  mass? 

19.  25  grams  oxalic  acid  yield  what  volume  of  CO  at  10°  and  740 
millimeters  pressure? 

20.  To  burn  one  gram  of  CS2  requires  what  volume  of  O? 

21.  What  volume  of  air  is  required  to  burn  one  liter  of  CN? 

22.  What  are  the  analogies  of  cyanogen  ? 

§2. 

23.  Give  the  method  of  preparation  and  the  properties  of  silicon. 

24.  Into  what  classes  are  the  silicates  divided  ?     Illustrate. 


PROPERTIES  OF  BORON.  257 


CHAPTEE   SIXTH. 

§  1.    BORON. 

Symbol  B.     Atomic  mass  10 '95.     Valence  ill.     Molecular  mass 
21-90  .(?).     Molecular  volume  2.     Specific  gravity  2 '68. 

339.  History  and   Occurrence.  —  Under  the  Arabic 
name  buraq,  corrupted  into  borax,  a  salt  obtained  from  cer- 
tain lakes  in  Thibet,  and  containing  boron  as  an  essential 
component,   has   long   been   imported    into   Europe.     From 
this,  in  1702,  Homberg-   obtained  boric   oxide ;    and  from 
boric  oxide,  Davy,  in  1807,  by  the  aid  of  electricity,  and 
Gay-Lussac    and   Thenard,  in  1808,  by  chemical  means, 
obtained  pure  boron.     It  \vas  first  obtained  crystallized  by 
Wohler  and  Deville  in  1856.     The  mineral  sassolite  is  boric 
acid,  H;jBO.H;  and  borax,  boracite,  and  larderellite  are  native 
borates  of  sodium,  magnesium,  and  ammonium  respectively. 

340.  Preparation  and  Properties. — Amorphous  boron 
may  be  prepared  by  the  action  of  sodium  upon  potassium 
fluoborate,  thus : 

(KBF4),  +  NaH  =  (KF),  +  (NaF)6  +  B2 
In  this  form  boron  is  a  soft,  greenish-brown  powder,  read- 
ily oxidized  by  nitric  acid,  and  fusible  at  the  heat  of  the 
oxy-hydrogen  flame.  It  may  be  obtained  crystallized  by  dis- 
solving it  in  melted  aluminum,  allowing  the  mass  to  cool, 
and  removing  the  aluminum  by  hydrochloric  acid.  Short 
quadratic  octahedrons  are  left  undissolved,  which  vary  from 
honey-yellow  to  garnet-red  in  color,  have  a  specific  gravity 
of  2-63,  and  are  nearly  as  hard,  as  lustrous,  and  as  highly 
refractive  as  the  diamond  itself.  These  crystals  contain  a 
little  aluminum,  are  infusible,  and  are  combustible  with  dif- 


258  INOKGAXIC  CHEMISTRY. 

ficulty  even  in  oxygen.  They  are  not  attacked  by  melted 
niter.  The  so-called  graphitoidal  boron  is  a  compound  of 
boron  and  aluminum. 

341.  Hydrogen  Boride,  H3B. — A  compound  of  hydro- 
gen and  boron  has  been  obtained  by  acting  on  magnesium 
boride  with  hydrogen  chloride.     A  colorless  gas  is  set  free, 
which  burns  with  a  bright  green  flame,  with  separation  of 
boric  oxide.     Upon  holding  a  cold  porcelain  surface  in  the 
flame,  a  brown  coating  of  boron  is  deposited  on  it.     Con- 
ducted into  silver-nitrate  solution,  it  produces  a  black  pre- 
cipitate in  it  consisting  of  silver  and  boron. 

342.  Boric  Oxide,  B2O3. — Boric  oxide  is  formed  when- 
ever boron  burns  in  the  air  or  in  oxygen.     It  is  usually  ob- 
tained by  igniting  its  hydrate,  boric  acid.     A  viscid  mass  is 
left,  which  solidifies  to  a  colorless,  brittle,  transparent  glass, 
of  specific  gravity  1  '83.     It  unites  directly  with  positive  ox- 
ides to  form  borates,  expelling  the  more  volatile  negative 
oxides  with  which  they  are  combined. 

343.  Boric  Acid,  H3BO3. — Boric  acid  occurs  free  in  na- 
ture, especially  in  volcanic  districts,  as  in  Tuscany,  where  it 
issues,  with  steam  and  gaseous  matters,  from  fissures  in  the 
earth,  into  natural  or  artificial  ponds  or  lagoons,  the  water 
of  which  soon  becomes  charged  with  the  acid.     This  water  is 
then  evaporated  and  the  acid  crystallized  out.     Boric  acid 
may  be  prepared  from  sodium  borate  or  borax,  by  dissolving 
three  parts  of  it  in  twelve  of  boiling  water,  adding  one  part 
of  sulphuric  acid,  and  allowing  the  whole  to  cool.    The  boric 
acid  separates  in  white  crystalline  scales,  of  specific  gravity 
1-48,  soluble  in  two  and  a  half  parts  of  water  at  18°,  and 
freely  soluble  in  alcohol.     Its  aqueous  solution  reddens  lit- 
mus paper  and  turns  turmeric  paper  brown.     Its  solution 
in  alcohol  burns  with  a  green  flame.     This  is  the  normal  or 
ortho-boric  acid.     By  heating  it  to  120°  it  loses  one  mole- 
cule of  water  and  yields  meta-boric  acid,  HBO2.    Boric  acid 
shows  a  strong  tendency  to  condensation,  thus  forming  mul- 


PEE  P.  I  If  A  TION  OF  AL  UMINUM.  259 

tiple  salts.  Borax,  or  sodium  tetraborate,  Na,2B4OT,  is  an 
example.  It  is  found  native  in  the  waters  of  certain  lakes 
in  Thibet  and  California.  It  is  used  largely  as  a  flux  in 
working  metals.  Boron  acts  in  some  cases  as  a  basic  ele- 
ment. Salts  of  this  element  are  known,  such  as  the  disul- 
phate  (BO)HS2O7  and  the  phosphate  BPO4. 

§  2.   ALUMINUM. 
Symbol  Al.     Atomic  mass  27*04.     Valence  III. 

344.  History  and  Occurrence. — Aluminum  oxide,  or 
alumina,  was  long  confounded  with  lime,  from  which  it  was 
first  distinguished  by  Marggraff  in  1754.    Oersted,  in  1826, 
first  prepared  the  chloride ;  and  from  this,  in  1828,  Wohler 
obtained  the  metal.     His  process  was  made  a  commercial 
one  by  St.  Claire  Deville  in  1854.    The  metal  was  first  pre- 
pared from  cryolite  by  H.  Rose  in  1855. 

Aluminum,  next  to  oxygen  and  silicon,  is  the  most  abun- 
dant element  in  nature.  The  minerals  corundum,  ruby,  and 
sapphire  are  aluminum  oxide ;  diaspore,  chrysoberyl,  and 
spinel  are  aluminates ;  micas,  feldspars,  and  clays  are  alu- 
minum silicates ;  cryolite  is  sodium-aluminum  fluoride ;  and 
many  other  minerals  contain  it  as  an  essential  constituent. 
Its  name  comes  from  the  Latin  alumen,  alum,  which  sub- 
stance was  largely  imported  into  Europe  from  the  East  until 
the  fifteenth  century. 

345.  Preparation  and  Properties. — Aluminum  is  gen- 
erally prepared  commercially  by- the  process  of  Deville,  which 
consists  in  reducing  the  chloride  with  sodium.    At  the  works 
of  Morin,  in  Paris,  ten  parts  sodio-aluminum  chloride,  five 
parts  of  fluor-spar  or  cryolite,  and  two  parts  of  sodium  are 
mixed  together  and  thrown  upon  the  hearth  of  a  reverber- 
atory  furnace,  previously  heated  to  full  redness.     A  violent 
action  takes  place,  great  heat  is  evolved,  and  the  liquefied 
mass  of  slag  and  metal  collects  at  the  back  of  the  furnace. 


260  INORGAXIC  CHEMISTRY. 

The  latter  is  drawn  off  and  cast  into  ingots.  This  process 
has  recently  been  greatly  improved  by  Castner.  Tissier,  at 
Amfreville,  makes  aluminum  from  the  mineral  cryolite,  after 
the  method  proposed  by  H.  Rose ;  and  in  this  country  it  Ls 
now  made  in  considerable  quantity  from  the  same  mineral 
by  electrolysis,  by  a  process  devised  by  Hall. 

Aluminum  is  a  brilliant  bluish-white  metal,  capable  of 
taking  a  fine  polish.  It  crystallizes  in  octahedrons,  and  con- 
ducts heat  and  electricity  readily.  It  is  highly  sonorous,  is 
very  light,  specific  gravity  2 '56  to  2-67,  and  is  very  mallea- 
ble and  ductile.  Its  tenacity  is  about  equal  to  that  of  silver, 
and  it  is  slightly  magnetic.  After  fusion  it  is  soft,  but  be- 
comes hard  by  hammering.  It  melts  at  a  temperature  of 
700°,  but  little  above  the  fusing-poiut  of  zinc,  but  is  not 
volatile.  It  tarnishes  very  slowly  in  the  air,  though  it  burns 
readily  in  thin  leaves  when  heated  in  oxygen.  Sulphuric 
and  nitric  acids  are  without  action  upon  it,  though  hydro- 
chloric acid  and  alkali-hydrates  attack  it  readily. 

Aluminum  is  used  in  the  arts  chiefly  for  ornamental  pur- 
poses, for  which  its  luster,  its  whiteness,  and  its  unalterabil- 
ity  in  the  air  well  adapt  it.  Its  lightness  makes  it  useful 
for  weights,  and  for  astronomical  and  physical  instruments. 
Culinary  utensils  have  also  been  made  of  it.  Alloyed  with 
copper,  it  forms  aluminum-bronze,  which,  when  it  contains 
ten  per  cent  of  aluminum  to  ninety  of  copper,  is  hard,  mal- 
leable, as  tenacious  as  steel,  and  takes  a  fine  polish. 

COMPOUNDS    OF  ALUMINUM. 

346.  Aluminum  Chloride. — Formula  AlCl.r  The  com- 
pounds of  aluminum  until  recently  were  supposed  to  contain 
this  element  with  a  double  atom.  But  the  latest  vapor-den- 
sity determinations,  particularly  of  its  organic  compounds, 
seem  to  establish  its  triad  character,  and  thus  to  confirm  the 
indications  of  the  periodic  series.  Aluminum  chloride  is 
prepared  by  passing  chlorine  over  an  ignited  mixture  of  the 


ALUMINUM  OXIDE  AND  SALTS.  261 

oxide  and  charcoal.  It  is  a  colorless,  semi-crystalline,  waxy 
substance,  fusible  and  volatile,  and  having  a  vapor-density 
of  134.  It  combines  violently  with  water,  forming  the  hy- 
drate A1C13,  6  aq.  Chlorine,  passed  over  an  ignited  mixture 
of  salt,  aluminum  oxide,  and  charcoal,  yields  sodio-alumi- 
num  chloride,  NaAlCl4,  as  a  white  crystalline  solid,  which 
melts  at  200°.  Aluminum  fluoride,  A1F3,  combined  with 
sodium  fluoride,  occurs  native  in  the  mineral  cryolite. 

tt47.  Aluminum  Oxide.— Formula  A12O3.— Aluminum 
oxide  occurs  native  in  the  mineral  corundum,  which  includes 
the  precious  stones  known  as  the  ruby  and  the  sapphire,  as 
well  as  the  valuable  polishing  material  called  emery.  It  may 
be  prepared  by  the  combustion  of  the  metal  in  oxygen  or 
by  igniting  the  hydrate.  It  is  found  in  nature  crystallized 
in  rhombohedral  forms,  with  a  specific  gravity  of  3 '90,  and 
scarcely  inferior  in  hardness  to  the  diamond.  Aluminum 
hydrate,  A1(OH)3,  or  ortho-aluminic  base,  occurs  native  as 
gibbsite.  It  is  obtained  by  precipitating  any  salt  of  alumi- 
num by  ammonium  hydrate.  Meta-aluminic  base  AIO(OH) 
is  also  known,  occurring  in  nature  as  the  mineral  diaspore. 
Aluminic  hydrate  acts  as  an  acid  with  basic  radicals,  forming 
aluminates ;  sodium  ortho-aluminate,  Na3AlO3,  and  rneta- 
aluminate,  NaAlO2,  and  potassium  meta-aluminate,  KA1O2, 
have  been  prepared  artificially ;  and  beryllium  aluminate,  Be" 
(A1O2)2,  or  chrysoberyl ;  magnesium  aluminate,  Mg"(AlO2)2, 
or  spinel ;  and  zinc  aluminate,  Zn"(AlO2)2,  or  gahnite,  are 
well-known  minerals.  With  strong  acids,  aluminum  hydrate 
acts  as  a  base.  With  sulphuric  acid,  it  yields  aluminum 
sulphate,  A12(SO4)3, 18  aq.,  the  mineral  alunogen;  it  is  used 
in  dyeing.  It  forms  a  characteristic  class  of  double  sulphates 
called  alums,  whose  general  formula  is  MA1(SO4)2,  12  aq.,  M 
being  generally  K  or  (NH4).  They  all  crystallize  in  regular 
octahedrons,  are  acid  in  their  reaction,  and  have  a  styptic 
taste.  Aluminum  phosphate,  A1(PO4),  is  known  in  the 
hydrated  form.  The  silicates  of  aluminum  constitute  an 

18 


262  INORGANIC  CHEMISTRY. 

important  class  of  minerals.  Orthoclase  is  a  potassio-alumi- 
num  silicate,  albite  a  sodio-aluminum  silicate,  and  labrador- 
ite  a  calcio-aluminum  silicate.  Clay  is  a  more  or  less  pure 
aluminum  silicate,  Al2Si.2O7,  2  aq.  It  is  used  in  pottery,  the 
finer  kinds  being  known  as  kaolin,  or  porcelain  clay. 

RELATIONS    OF   THE   GROUP. 

348.  To  this  group  belong  also  scandium,  yttrium,  lan- 
thanum, and  ytterbium,  all  rare  elements.  They  are  all 
trivalent  and  form  similar  compounds.  Boron  is  the  most 
strongly  negative,  and  the  acidic  character  seems  to  diminish 
as  the  atomic  mass  increases ;  so  that  ytterbium  would  be 
the  most  strongly  positive.  The  intermediate  electro-chem- 
ical character  of  the  group  appears  in  the  fact  that,  while 
boron  gives  an  acid  hydrate,  B(OH):i,  aluminum  gives  a 
basic  one,  A1(OH)3;  taken  in  connection  with  the  further 
fact  that  BPO4  is  as  stable  a  salt  as  magnesium  aluminate, 
Mg(AlO2).2 ;  and  yet  in  the  latter  compounds  the  electro- 
chemical character  is  reversed. 


EXERCISES.  263 


EXERCISES. 


1.  In  what  forms  does  boron  occur? 

'2.  How  is  hydrogen  boride  prepared? 

8.  What  mass  of  B.20;5  can  be  obtained  from  10  grams  of  borax? 

4.  Write  the  constitutional  formula  of  borax. 


5.  In  what  compounds  does  aluminum  occur  in  nature? 

6.  Give  the  process  adopted  by  Morin  for  preparing  it. 

7.  Cryolite  has  the  formula  NaaAlF6;  what  per  cent  of  aluminum 
does  it  contain? 

8.  What  is  the  mass  of  an  aluminum  ball  5  centimeters  in  diam- 
eter ? 

9.  Write  the  graphic  formula  of  aluminum  chloride.    Oxide. 

10.  Under  what  names  does  aluminum  oxide  occur? 

11.  Calculate  the  percentage  composition  of  the  mineral  cbryso- 
beryl. 

12.  Fibrolite  contains  36-8  per  ce:it  of  silicic  oxide  and  63-2  per 
cent  of  aluminum  oxide;  what  is  its  formula?    (Molecular  mass  163.) 


264  INORGANIC  CHEMISTRY. 


CHAPTER   SEVENTH. 

POSITIVE  TETKADS. 

§  1.   TIN. 

Symbol  Sn.     Atomic  mass  117*8.     Valence  II  and  IV.     Molec- 
ular mass  235-6  (?). 

349.  History  and  Occurrence. — Tin  has  been  known 
from  the  remotest  antiquity.    It  is  spoken  of  by  Moses  (Num- 
bers, xxxi,  22) ;  and  Homer  mentions  it  in  the  Iliad  under 
the  name  xaffffirepo-.     Much  of  the  brass  of  the  ancients  was 
a  copper  and  tin  bronze,  the  tin  being  obtained  from  Corn- 
wall ;  whence  Herodotus  speaks  of  the  British  Isles  as  the 
xaffffiTzptdzq  or  tin-islands.    The  principal  ore  of  tin  is  stannic 
oxide,  known  as  the  mineral  cassiterite.     It  occurs  in  veins 
running  through  ancient  rocks — vein  or  mine-tin — and  also 
in  the  beds  of  water-courses,  from  the  disintegration  of  these 
rocks  —  stream  tin.     The  principal  localities  of  tin  ore  are 
Cornwall,  England,  and  Banca  and  Malacca,  India.     It  has 
been  found  in  New  Hampshire   and  in  California  in  this 
country. 

350.  Preparation  and  Properties.  —  The  ore  is  pul- 
verized, roasted,  and  washed,  and  is  then  smelted  with  char- 
coal, which  removes  the  oxygen.     It  is  refined  by  melting 
and  thrusting  into  it  a  stick  of  wet  wood ;   the  impurities 
rise  to  the  surface  and  are  skimmed  off.     The  tin  is  then 
ladled  into  molds,  the  upper  layers  being  the  purest.     It 
comes  into  commerce  as  grain-tin,  in  irregular  fragments 
produced  by  allowing  the  hot  ingots  to  fall  from  a  height ; 
and  as  block-tin,  a  less  pure  form,  in  ingots.     The  purest 


PREPARATION  OF  STANNIC  CHLORIDE.  265 

tin  is  imported  from  the  island  of  Banca,  and  is  known  as 
straits-tin. 

Tin  is  a  soft,  brilliant-white  metal,  of  specific  gravity  7*29. 
It  is  dimorphous,  crystallizing  in  forms  belonging  to  the  iso- 
metric and  the  quadratic  systems.  It  is  very  malleable,  and 
may  be  beaten  into  leaves  one  fortieth  of  a  millimeter  thick ; 
at  100°  it  is  ductile  and  may  be  drawn  into  wire.  Its  tenac- 
ity, however,  is  small.  It  crackles  when  a  bar  of  it  is  bent, 
producing  what  is  known  as  the  cry  of  tin.  It  has  a  pecul- 
iar odor,  and  is  a  good  conductor  of  heat  and  electricity.  It 
melts  at  230°,  and  distills  at  a  white  heat.  Heated  in  the 
air,  it  burns  readily  to  oxide,  though  it  retains  its  luster  in 
air  at  ordinary  temperatures.  Acids  attack  it  readily. 

351.  Uses. — Tin  is  used  in  the  arts  for  making  tin  foil, 
for  covering  iron  in  the  preparation  of  tin  plate,  and  for 
alloys.    Pewter,  britannia,  queen's  metal,  and  solder  are  alloys 
of  tin  and  lead,  containing  sometimes  a  little  antimony  and 
bismuth.    Bell-metal,  gun-metal,  bronze,  and  speculum-metal 
are  essentially  alloys  of  tin  and  copper.     In  gun-metal  and 
bronze,  the  tin  constitutes  one  part  in  ten  or  twelve,  in  bell- 
metal  one  part  in  five,  and  in  speculum -metal  one  part  in 
three. 

TIN   AND    CHLORINE. 

STANNIC  CHLORIDE. — Formula  SnCl4.   Molecular  mass  259 -28. 

352.  Preparation  and  Properties. — Stannic  chloride 
— known  to  the  alchemists  as  Liquor  fumans  Libavii — may 
be  obtained  by  the  direct  action  of  chlorine  gas  upon  tin,  or 
by  distilling  mercuric  chloride  with  tin  filings : 

(HgCl2)2  +  Sn  =  Hg,2  +  SnCl, 

It  is  a  colorless,  fuming  liquid,  of  specific  gravity  2 '28,  which 
boils  at  115°.  Its  vapor-density  is  130.  It  unites  with  water 
readily,  evolving  heat,  and  forming  two  crystalline  hydrates. 
With  alkali-chlorides  it  forms  definite  compounds,  the  potas- 
sium salt  being  K.2SnCl(i.  It  is  used  in  dyeing. 


266  INORGANIC  CHEMISTRY. 

STANNOUS    CHLORIDE.  —  Formula   SnCL,.       Molecular   mas* 
188-54. 

353.  Preparation  and  Properties. — Stannous  chloride 
may  be  prepared  by  distilling  tin  filings  with  mercurous  chlo- 
ride, or  by  the  action  of  heat  upon  its  hydrate.    It  is  a  gray- 
ish-white translucent  solid,  which  melts  at  250°,  and  may  be 
distilled  at  620°;  at  900°  its  vapor-density  is  normal.     By 
solution  in  water  and  evaporation,  large  colorless  monoclinic 
prisms  are  produced,  having  the  composition  SnCl2,  2  aq. 
These  crystals  are  known  as  the  " tin-salt"  of  the  dyer,  for 
whose  use  they  are  commonly  made  by  dissolving  metallic 
tin  in  hydrochloric  acid.     Stannous  chloride  is  used  in  the 
laboratory  as  a  reducing  agent. 

TIN    AND    OXYGEN. 

STANNIC  OXIDE. — Formula  SnlvO2.     Molecular  mass  149-72. 

354.  Preparation  and  Properties. — Stannic  oxide  oc- 
curs native  as  the  mineral  cassiterite,  or  tin-stone,  crystal- 
lized in  square  prisms,  terminated  by  the  faces  of  the  square 
octahedron.     It  may  be  prepared  by  burning  the  metal  in 
air,  or  by  igniting  either  of  the  hydrates.    It  is  then  obtained 
as  a  white  powder,  of  specific  gravity  6 -6,  insoluble  in  all 
acids  except  hydrofluoric.     Owing  to  its  hardness  it  is  used 
for  polishing  glass,  under  the  name  of  putty-powder.     When 
fused  with  alkali-hydrates  it  forms  stannates. 

355.  Stannic  Acids.— Oriho  H4SnO4  and  Meta  H2SnO:,. 
Ortho-stannic  acid  is  precipitated  from  alkaline  stannates  by 
acids,  or  from  stannic  chloride  by  ammonia,  as  a  gelatinous 
mass,  which  loses  water  on  drying  in  vacuo,  and  becomes 
meta-stannic  acid.     When  tin  is  oxidized  by  nitric  acid,  a 
polymeric  form  of  meta-stannic  acid  is  produced,  which  when 
dried  at  100°  has  the  formula  H10Sn.O15.     Sodium  meta-stan- 
nate  Na2SnO3,  3  aq.,  made  by  fusing  native  tin-stone  with 
sodium  hydrate,  is  used  as  a  mordant  in  dyeing. 


HlSTOliY  JA7>  (MT-rilRENCE  OF  LEAD.  267 

STANNOUS  OXIDE. — Formula  Sn"0.     Molecular  mass  133-76. 

356.  Preparation  and  Properties. —  Stannous  oxide 
is  obtained  when  stannous  oxalate  is  heated  in  close  vessels. 
It  is  a  black  powder  of  specific  gravity  6 '6,  crystallizing  in 
the  isometric  system,  and  combustible  when  heated  in  the 
air.     With  water  it  forms  a  ^hydrate  which  absorbs  oxygen 
gradually  from  the  air,  and  passes  into  stannic  acid.    With 
sulphuric  acid  it  forms  stannous  sulphate  Sn"SO4. 

TIN    AND    SULPHUR. 

STANNIC  SULPHIDE. — Formula  SnlvS2.    Molecular  mass  181  -76. 

357.  Preparation  and  Properties. — Stannic  sulphide 
is  prepared  by  heating  together  tin-amalgam,  sulphur,  and 
ammonium  chloride  (sal-ammoniac).     A  golden-yellow  crys- 
talline powder  having  a  metallic  luster  and  a  specific  gravity 
of  4'6  is  left  in  the  vessel.     This  substance  was  known,  to 
the  alchemists  under  the  name  of  aurum  musivum,  or  mosaic 
gold.     It  is  used  as  a  bronze-powder. 

§  2.  LEAD. 

Symbol  Pb.    Atomic  maw  206 '4.     Valence  II  and  IV.     Specific 
gravity  11*37. 

358.  History  and  Occurrence. — Lead  has  been  known 
from  the  earliest  ages  of  history.     It  is  mentioned  in  the 
book  of  Job  and  elsewhere  in  the  sacred  writings.    The  Ro- 
mans worked  the  lead  ores  of  Spain  and  of  England,  and 
the  Carthaginians  those  of  Spain,  the  extent  of  their  mining 
and  smelting  operations  exciting  surprise,  even  at  the  pres- 
ent day.    The  principal  workable  ore  of  lead  is  its  sulphide, 
or  galenite ;  though  it  occurs  also  somewhat  abundantly  as 
carbonate,  or  cerussite ;  as  sulphate,  or  anglesite ;  as  chloro- 
arsenate,  or  mimetite  ;  as  chloro-phosphate,  or  pyromorphite  ; 
and  in  other  forms. 

** 


268  INORGANIC  CHEMISTRY. 

359.  Preparation  and  Properties. — Lead  is  prepared 
from  the  sulphide  by  a  comparatively  simple  metallurgical 
process.  The  ore  is  first  roasted  on  the  floor  of  a  reverbera- 
tory  furnace,  by  which  both  oxide  and  sulphate  of  lead  are 
produced.  The  furnace  is  then  closed  tight,  and  these  prod- 
ucts react  upon  the  undecomposed  lead  sulphide  as  follows : 

(PbO)2     +     PbS      =       S02      +      Pb3 

Lead  oxide.        I^ead  sulphide.    Sulphurous  oxide.        Lead. 

PbSO4     +      PbS     =      (S02)2    +     Pb2 

Lead  sulphate.       Lead  sulphide.      Sulphurous  oxide.       Lead. 

When  the  ore  contains  impurities,  it  is  smelted  by  fusing  it 
with  iron,  ferrous  sulphide  and  lead  being  produced.  Other 
methods  are  employed  for  smelting  lead,  varying  according 
to  the  ore  and  the  locality. 

Lead  is  a  brilliant  metal,  bluish-white  in  color,  and  so 
soft  as  to  be  easily  cut  with  a  knife.  It  leaves  upon  paper 
a  bluish-gray  streak,  and  is  very  malleable.  It  has  a  spe- 
cific gravity  of  11*37,  crystallizes  in  regular  octahedrons, 
and  fuses  at  325°.  At  a  white  heat  it  may  be  distilled.  It 
has  but  a  feeble  tenacity,  a  wire  two  millimeters  in  diameter 
sustaining  only  nine  kilograms.  A  freshly  cut  surface  tar- 
nishes in  ordinary  air,  but  remains  bright  in  perfectly  dry 
air  and  also  in  water  free  from  air.  Potable  waters  in  gen- 
eral act  upon  lead,  dissolving  it,  and  partly  precipitating  it 
as  carbonate.  This  action  is  particularly  noticeable  in  well- 
waters  which  contain  nitrates  from  decomposed  animal  mat- 
ter, or  chlorides  from  saline  infiltration.  Lead  water-pipes 
should  therefore  be  avoided  or  used  with  great  caution.  When 
melted  in  the  air,  lead  is  rapidly  converted  into  the  oxide. 
It  is  scarcely  attacked  by  sulphuric  or  hydrochloric  acid  at 
ordinary  temperatures,  but  dissolves  readily  in  nitric  acid. 
In  presence  of  air  and  moisture  it  is  acted  upon  by  quite 
feeble  acids,  as  acetic  and  carbonic.  Hence  the  use  of  such 
vessels  as  are  made  of  or  are  united  with  lead,  or  lead  solder, 


PROPERTIES  OF  LEAD.  269 

should  be  avoided  for  such  articles.  Lead,  when  taken  into 
the  system,  unites  definitely  with  certain  tissues  and  is  re- 
tained there,  until  finally  sufficient  accumulates  to  produce 
poisoning.  Acute  colic  is  characteristic  of  poisoning  by  a 
large  dose  of  lead ;  but  in  chronic  poisoning,  which  is  far 
more  common,  there  is  paralysis,  particularly  of  the  muscles 
of  the  forearm,  causing  the  wrists  to  drop;  or  there  may 
be  simply  an  indefinable  feeling  of  malaise,  accompanied  by 
dyspeptic  symptoms. 

Lead  is  used  extensively  in  the  arts  for  various  purposes, 
both  alone  and  alloyed  with  other  metals.  With  a  small 
proportion  of  arsenic  it  forms  the  alloy  of  which  shot  are 
made ;  with  antimony  and  tin,  it  forms  type-metal ;  with  bis- 
muth, the  soft  alloy  used  for  permanent  pencil-points ;  with 
tin,  pewter  and  soft  solder ;  and  with  cadmium,  tin,  and  bis- 
muth, fusible  metal  melting  at  60°. 

EXPERIMENT. — Metallic  lead  in  a  state  of  fine  division  takes  fire 
readily  in  the  air,  forming  what  is  known  as  pyrophorus.  To  obtain 
it  in  this  form,  tartrate  of  lead  is  produced  by  adding  lead  acetate  to 
a  solution  of  potassio-sodium  tartrate  —  rochelle  salt — so  long  as  it 
forms  a  precipitate.  The  lead  tartrate,  filtered  off,  washed,  and  dried, 
is  placed  in  a  tube  of  hard  glass,  the  tube  is  then  drawn  out  at  the 
end,  and  the  whole  is  heated  to  a  bright  redness,  until  no  more  fumes 
escape.  The  end  of  the  tube  is  then  sealed,  and  the  whole  allowed 
to  cool.  On  breaking  the  tube  and  pouring  out  the  contents  into  the 
air,  the  metallic  lead  at  once  inflames,  producing  a  shower  of  fire.  In 
oxygen  the  combustion  is  brilliant;  in  carbon  di-oxide  no  combustion 
takes  place. 

LEAD    AND    CHLORINE. 

360.  Plumbic  Chloride.— Form ula  Pb"Cl,.— This  chlo- 
ride has  been  found  in  the  crater  of  Vesuvius  after  an  erup- 
tion, and  is  known  as  cotunnite.  It  is  precipitated  from  any 
plumbic  solution,  if  sufficiently  concentrated,  upon  the  addi- 
tion of  hydrochloric  acid  or  a  chloride.  It  is  a  heavy  white 
powder,  soluble  in  135  parts  of  cold  and  30  parts  of  boiling 
water,  from  which  it  crystallizes,  on  cooling,  in  lustrous  nee- 


270  INORGANIC  CHEMISTRY. 

dies.  It  melts  when  heated  in  close  vessels,  and  at  a  higher 
temperature  sublimes.  The  fused  chloride  is  translucent  and 
sectile,  and  is  known  as  horn-lead.  A  white  and  a  yellow 
oxy-chloride  are  used  as  pigments. 

361.  Plumbic  Per-chloride.— Formula  PblvCl4.— Plum- 
bic per-chloride  is  obtained  in  solution  by  dissolving  plumbic 
peroxide  in  cold  hydrochloric  acid,  and  in  crystals  by  evap- 
orating this  solution  in  vacuo.    It  has  been  but  little  studied. 

LEAD   AND    OXYGEN. 

362.  Plumbic  Peroxide.— Formula  PblvO2.  —  Plumbic 
peroxide  is  best  prepared  by  precipitating  a  solution  of  four 
parts  of  lead  acetate  with  a  solution  of  three  and  a  half 
parts  of  crystallized  sodium  carbonate,  and  passing  chlorine 
gas  through  the  mixture  until  the  whole  of  the  white  car- 
bonate of  lead  is  converted  into  the  brown  peroxide.     It 
forms  on  drying  a  chocolate-brown  or  puce-colored  powder, 
which  gives  off  oxygen  on  heating.     It  is  a  strongly  oxidiz- 
ing agent,  uniting  directly  with  sulphurous  oxide  to  form 
plumbic  sulphate.  .Digested  with  ammonic  hydrate,  it  forms 
water  and  lead  nitrate ;  mixed  with  one  fifth  its  weight  of 
sulphur,  it  inflames  spontaneously ;  rubbed  in  a  mortar  with 
one  sixth  of  grape-sugar  ignition  takes  place ;  it  sets  iodine 
free  from  potassium  iodide,  and  bleaches  a  solution  of  sulph- 
indigotic  acid. 

Plumbic  peroxide  combines  directly  with  the  oxides  of  po- 
tassium, sodium,  calcium,  and  even  lead,  forming  salts  called 
plumbates,  having  the  general  formula  M,PbO.,.  Potassium 
plumbate  occurs  in  white  "octahedrons,  decomposable  by  wa- 
ter. Plumbic  plumbates  form  the  various  compounds  knowTn 
as  red-leads.  The  compound  Pb".2PblvO4,  or  plumbic  ortho- 
plumbate,  written  more  often  Pb.?O4,  occurs  native  as  min- 
ium. This,  as  well  as  the  meta-plumbate  Pb"PblvO,,  or  Pb.2O,, 
is  produced  largely  in  the  arts  as  a  pigment,  by  oxidizing 
litharge  in  a  current  of  air,  and  then  cooling  very  slowly. 


PLUMBIC  OXWK  JA7)  HYDUATE.  271 

Nitric  acid  decomposes  these  plumbates,  producing  lead  ni- 
trate and  plumbic  peroxide.  The  same  result  is  produced 
by  much  weaker  acids,  such,  for  example,  as  acetic  acid. 

363.  Plumbic  Oxide.—  Formula  Pb"O.—  This  oxide  of 
lead  occurs  native  as  the  mineral  massicot.  It  is  prepared 
on  the  large  scale  in  the  arts  under  the  name  of  litharge,  by 
heating  melted  lead  in  a  current  of  air.  Its  color  is  pale- 
yellow,  or  orange-yellow,  according  to  the  temperature  at 
which  it  is  produced.  It  is  dimorphous,  crystallizing  in 
rhombic  octahedrons  and  in  regular  dodecahedrons.  Its  spe- 
cific gravity  is  9*42,  and  infuses  at  a  full  red  heat.  It  is 
soluble  only  in  7,000  parts  of  water,  but  acids  dissolve  it 
easily,  forming  definite  salts.  It  is  also  soluble  in  alkali- 
hydrate  solutions,  and  in  lime-water.  It  is  used  in  the  arts 
in  the  manufacture  of  glass. 

Plumbic  hydrate,  H.,PbO.,  or  Pb"(OH)2,  is  known  only  as 
a  colorless,  sweetish,  alkaline  liquid,  obtained  by  the  action 
upon  lead  of  water  and  air,  free  from  carbon  di-oxide.  The 
precipitate  produced  by  hydrates  of  the  alkalies  in  plumbic 
solutions  is  an  oxy-hydrate  having  the  composition  Pb2O 
(OH),. 

Plumbic  nitrate,  Pb"(NO3)2,  is  produced  by  dissolving 
lead  or  its  oxide  in  nitric  acid  and  crystallizing.  The  hy- 


( 
dro-nitrate  H(NO2)'PbO2  or  Pb  j  \    is  precipitated 


from  the  nitrate  by  adding  ammonium  hydrate  in  small 
quantity.  Plumbic  carbonate,  PbCO3,  occurs  native  as 
cerussite;  a  hydro  -  carbonate,  Fb8(COg),(OH)t,  is  much 
used  as  a  pigment  under  the  name  of  white-lead.  Plumbic 
sulphate,  PbSO4,  which  occurs  native  as  anglesite,  is  pre- 
cipitated from  solutions  of  lead  on  adding  sulphuric  acid  or 
soluble  sulphates. 

364.  Plumbous  Oxide.  —  Formula  Pb2O.  —  When  lead 
oxalate  is  heated  to  300°  in  a  closed  vessel,  a  black  velvety 
powder  is  obtained,  which  is  plumbous  oxide.  It  contains 


272  INORGANIC  CHEMISTRY. 

no  metallic  lead  and  no  plumbic  oxide ;  but  takes  fire  when 
heated  in  the  air,  producing  this  oxide. 

RELATIONS    OF   THE   GROUP. 

365.  This  group  includes  germanium,  tin,  and  lead.  Ger- 
manium was  discovered  in  1886  by  Winkler,  in  a  Freiberg 
silver-ore,  and  is  remarkable  as  being  one  of  the  three  ele- 
ments whose  properties  were  predicted  by  Mendeleeff  by  the 
aid  of  the  periodic  law.  It  is  extremely  rare.  The  members 
of  the  group  are  closely  allied,  and  show  a  distinct  grada- 
tion of  properties  as  the  atomic  mass  increases,  germanium 
being  the  most  strongly  electro-negative  and  lead  the  most 
strongly  electro-positive.  They  all  form  halogen  compounds 
of  the  types  MX2  and  MX4,  and  oxygen  and  sulphur  com- 
pounds of  the  types  MO  and  MS,  MO,  and  MS, ;  the  latter 
acting  negatively  and  forming  salts  with  the  alkalies.  The 
hydrates  of  germanium  ancf  tin  act  as  weak  acids. 


EXERCISES.  273 


EXERCISES. 

1.  How  does  tin  occur  in  nature  ?     How  is  it  obtained  ? 

2.  What  mass  of  "  tin  salts  "  will  250  kilograms  of  tin  yield  ? 

3.  What  volume  of  chlorine  is  contained  in  a  gram  of  stannous 
chloride?     Of  stannic  chloride? 

4.  To  give  a  kilogram  of  stannic  sulphide  requires  what  mass  of 
tin? 

§2. 

5.  Mention  the  minerals  in  which  lead  occurs. 

6.  Write  the  chemical  reactions  which  take  place  in  obtaining 
lead  from  galenite. 

7.  1,000  kilograms  of  galenite  yield  what  volume  of  SO2? 

8.  What  mass  of  metallic  lead  would  be  obtained? 

9.  Calculate  the  volume  occupied  by  a  kilogram  of  lead. 

10.  What  are  the  objections  to  the  use  of  lead  water-pipes? 

11.  How  is  a  lead  pyrophorus  prepared  ? 

12.  What  volume  of  chlorine  is  contained  in  the  plumbic  chloride 
required  to  saturate  a  liter  of  water? 

13.  What  mass  of  sulphur  may  be  burned  by  one  gram  of  lead  di- 
oxide?    Write  the  reaction. 

14.  Give  the  rational  constitution  of  the  red-leads. 

15.  One  cubic  decimeter  of  lead  will  give  what  mass  of  litharge? 

16.  How  many  kilograms  of  white-lead  can  be  obtained  from  1,000 
kilograms  of  lead  ? 


274  INORGANIC  CHEMISTRY. 


CHAPTER   EIGHTH. 

THE  PLATINUM  GKOUP. 
$5  1.    PLATINUM. 

Symbol  Pt.     Atomic  mass  194*3.     Valence  II  and  IV. 

366.  History  and  Occurrence. — Platinum  was  brought 
to  Europe  from  South  America  in  1735  by  Ulloa,  and  in 
1741  by  Wood.     It  was  first  described  by  Watson  in  1750, 
and  independently  by  Scheffer  in  1752.     It  derives  its  name 
from  the  word  platina,  the  Spanish  diminutive  of  plata,  silver. 
It  occurs  native  usually  in  rounded  grains,  though  sometimes 
it  is  found  crystallized  in  octahedrons.     It  is  rarely  pure,  the 
native  platinum  containing  gold,  iron,  and  copper,  besides 
iridium,  ruthenium,  osmium,  rhodium,   and  palladium,  its 
natural  congeners.     It  occurs  not  only  in  South  America, 
but  also  in  Russia,  in  Borneo,  and  in  California. 

367.  Preparation  and  Properties. — Native  platinum 
was  formerly  purified  by  the  method  of  Wollaston,  which 
consists  in  treating  the  crude  metal  first  with   nitric  acid 
and  then  with  hydrochloric  acid,  and  afterward  with  boiling- 
aqua  regia.     By  the  latter  treatment,  the  platinum,  palla- 
dium, and  a  portion  of  the  rhodium  are  dissolved,  while  a 
mixture  of  iridium,  rhodium,  osmium,  and  ruthenium,  known 
as  iridosmine,  is  left.     The  platinum  is  thrown  down  from 
its   solution  by  ammonium  chloride,  as  ammonium  chloro- 
platinate.     This,  on  ignition,  leaves  the  metal  in  a  finely- 
divided    state  known   as  spongy  platinum,  which   is  con- 
densed into  a  cake  by  powerful  pressure,  and  is  then  welded 
at  a  white  heat  into  a  homogeneous  mass. 


PROPERTIES  OF  PLATINUM. 


275 


Latterly,  however,  Deville's  method  has  almost  entirely 
superseded  that  of  Wollaston.  In  this  the  crude  platinum 
is  melted  with  an  equal  weight  of  lead  sulphide  and  half 
its  weight  of  metallic  lead ;  in  this  way  the  platinum  is  dis- 
solved, leaving  the  iridosmine.  The  platinum-lead  alloy  is 
then  melted  and  exposed  to  a  current  of  air,  by  which  the 
lead  is  oxidized,  the  oxide  flowing  off  as  slag,  and  the  plati- 
num being  left  as  a  porous  mass.  This  is  then  placed  in 
a  furnace  made  of  lime  (Fig. 
98),  and  by  means  of  two 
powerful  oxy-hydrogen  jets,  it 
is  melted  and  cast  into  ingots. 
Masses  weighing  100  kilo- 
grams have  been  produced 
by  this  process  at  one  fusion. 
The  melted  mass  absorbs  oxy- 
gen, and  evolves  it  again  on 
cooling,  like  silver. 

Platinum  is  a  brilliant  white 
metal,  with  a  tinge  of  blue.  It  has  a  specific  gravity  of 
21-5,  is  extremely  malleable  and  ductile,  and  has  a  tenacity 
and  hardness  resembling  that  of  copper.  It  is  an  imperfect 
conductor  of  heat  and  of  electricity,  and  is  infusible  by  ordi- 
nary means,  but  yields  to  the  oxy-hydrogen  flame  (1775° ), 
in  which  it  is  partially  volatilized.  '  Before  complete  fusion 
it  softens,  and  may  then  be  welded.  At  high  temperatures 
it  absorbs  hydrogen,  and  is  readily  permeable  by  this  gas  at 
a  red  heat.  Platinum  is  unaltered  in  the  air  at  any  tem- 
perature ;  it  is  not  attacked  by  any  single  acid,  being  dis- 
solved only  by  aqua  regia.  Fused  potassium  and  sodium 
hydroxides  act  upon  it ;  and  it  combines  directly  with  sul- 
phur, phosphorus,  arsenic,  and  silicon. 

Platinum  possesses  in  a  remarkable  degree  the  property 
of  condensing  gases  upon  its  surface.  In  the  form  of  plati- 
num-foil, it  will  cause  the  explosion  of  mixed  oxygen  and 


Fig.  98.  Platinum  Furnace. 


276  INORGANIC  CHEMISTRY. 

hydrogen  gases;  but  in  the  form  of  platinum-sponge  it  is 
much  more  active  ;  and  in  the  still  more  finely  divided  form 
known  as  platinum  black,  it  is  capable  of  absorbing  800 
times  its  volume  of  oxygen.  Platinum  black,  therefore, 
owing  to  this  condensed  oxygen,  is  an  energetic  oxidizing 
agent ;  alcohol  thrown  upon  it  is  at  once  inflamed.  From 
recent  researches,  Berthelot  regards  platinum  black  as  a  sub- 
oxide.  When  hydrogen  acts  on  it,  it  first  reduces  this  oxide 
and  then  forms  a  hydride  with  the  metal. 

Owing  to  its  infusibility  and  its  unalterability  by  chemical 
agents,  platinum  is  used  extensively  both  in  the  arts  and  in 
the  laboratory  for  chemical  vessels.  Large  platinum  stills  for 
sulphuric  acid  weigh  often  30,000  grams.  Platinum  has  been 
used  in  Russia  also  for  coinage. 

COMPOUNDS   OF   PLATINUM. 

368.  Platinum  Chlorides. — Two  chlorides  of  platinum 
are  known,  the  platinic  chloride,  PtCl4,  and  the  platinous 
chloride,  PtCL2.  The  former  is  obtained  whenever  platinum 
is  dissolved  in  aqua  regia.  By  evaporation  at  100°,  a  brown- 
red  deliquescent  mass  is  left,  soluble  freely  in  water,  alcohol, 
and  ether.  It  loses  half  its  chlorine  at  230°,  and  the  whole 
at  a  red  heat.  It  unites  directly  with  alkali  chlorides,  form- 
ing chloro  -  platinates,  M2PtClg.  Platinous  chloride  is  pro- 
duced by  heating  platinic  chloride  to  230°,  until . chlorine 
ceases  to  be  evolved.  A  dark-green  powder  is  left,  insoluble 
in  water,  sulphuric  and  nitric  acids,  but  soluble  in  sodium 
and  potassium  hydroxides.  A  series  of  remarkable  com- 
pounds is  formed  by  the  action  of  ammonia  upon  this  chlo- 
ride, called  the  ammonio-platinum  bases. 

369*  Platinic  Oxide,  PtO2,  forms  a  hydrate  Ptlv(OH)4, 
which  dissolves  in  alkali-hydrates,  yielding  platinites.  Pla- 
tinous oxide,  PtO,  yields  a  basic  hydrate  Pt"(OH)2,  which 
forms  salts  with  acids.  Platinous  and  platinic  sulphides 
are  also  known. 


RELATIONS  OF  THE  PLATINUM  GROUP.  277 

RELATIONS    OF   THE    GROUP. 

37O.  The  platinum  metals,  so  called,  are  commonly  di- 
vided into  two  sub-groups,  according  to  the  periodic  law. 
Sub-group  A  contains  osmium,  iridium,  and  platinum,  and 
sub-group  B,  ruthenium,  rhodium,  and  palladium.  The  mem- 
bers of  these  sub-groups  are  closely  related : 

SUB-GROUP  A.  SUB-GROUP  B. 

0.5  Ir  Pt  Ru  Ro  Pd 

At.  ms.    191-0         192-5  194-3  103-5         104-1         106-2 

Sp.  gr.       22-48         22-42         21-50  12-20         12-1  11-5 

the  atomic  masses  and  specific  gravities  being  nearly  the 
same  for  each  sub-group.  Ruthenium  and  osmium  are  more 
strongly  negative,  palladium  and  platinum  more  strongly 
positive. 


EXERCISES. 


1.  With  what  other  elements  is  platinum  associated? 

2.  By  what  two  methods  is  it  refined? 

3.  An  alloy  of  platinum  and  gold  has  a  specific  gravity  of  20; 
what  per  cent  of  platinum  does  it  contain? 

4.  What  remarkable  property  has  finely-divided  platinum? 

5.  What  pressure  would  condense  oxygen  as  it  is  condensed  by 
platinum  black? 

6.  One  gram  of  PtCl4  contains  what  volume  of  chlorine? 


I'.i 


278  INORGANIC  CHEMISTRY. 


CHAPTER  NINTH. 

THE  IKON  GROUP. 
(  SUB-GROUP  A.) 

CHROMIUM. 
Symbol  Cr.     Atomic  imi#*  52 -4").     Valence  II,  III,  and  VI. 

371.  History  and  Occurrence. —  Chromium  was  first 
recognized  as  a  distinct  substance  by  Vauquelin  in  1797,  in 
a  native  lead  chromate  from  Siberia.     Its  name  comes  from 
Zl)a)tj.a,  color,  because  most  of  its  compounds  are  brilliantly 
colored.     It  occurs  in  nature   in  the  mineral  chromite,  or 
chrome-iron,  a  ferroso-chromic  oxide ;  also  as  lead  chromate 
in  the  mineral  crocoite.     It  forms  the  coloring  matter  of  the 
emerald,  and  has  been  found  in  meteoric  irons. 

372.  Preparation  and  Properties. — Chromium  is  pre- 
pared by  reducing  its  oxide  by  charcoal ;  or  better,  by  re- 
ducing the  chloride  by  zinc  or  magnesium.     By  the  former 
method,  it  is  obtained  as  a  steel-gray  mass,  highly  infusible 
aud  extremely  hard ;  by  the  latter,  as  a  gray-green,  glisten- 
ing powder,  composed  of  minute  tetragonal  octahedrons,  of 
specific  gravity  6 '8.     It  is  unaltered  when  heated  in  dry  air, 
but  burns  in  oxygen.     It  is  not  magnetic. 

CHROMIUM    AND    CHLORINE. 

373.  Chromic   Chloride. — Formula  CrCL. — Chromic 
chloride    is  obtained  by  passing  chlorine  gas  over  ignited 
pellets  of  chromic  oxide  and  lamp-black.     A  sublimate  of 
micaceous  scales,  beautiful  peach-blossom  in  color,  and  of  an 
unctuous  feel,  is  thus  produced,  which  is  insoluble  in  water 


COMPOUXDS  OF  CHEOMIUM.  279 

unless  a  trace  of  chromous  chloride  is  present  ;  then  it  dis- 
solves readily.  It  is  unaltered  by  ordinary  re-agents.  On 
prolonged  boiling  with  water  it  dissolves,  forming  a  green 
solution,  containing  a  hydrate.  A  soluble  violet  modifica- 
tion is  produced  by  heating  the  green  hydrate  in  a  current 
of  hydrochloric  acid  gas.  Its  solution  becomes  green  on 
boiling.  The  chlorine  of  the  violet  solution  is  completely 
precipitated  by  silver  nitrate  ;  that  of  the  green  solution  but 
partially. 

374.  Chromous  Chloride.  —  Formula  CrCl.2.  —  Chromous 
chloride  is  prepared  by  reducing  chromic  chloride  by  hydro- 
gen at  a  gentle  heat.     It  is  a  white,  crystalline  substance, 
soluble  in  water,  forming  a  blue  solution,  which  by  absorp- 
tion of  oxygen  rapidly  becomes  green. 

375.  Chromic  Per-fiuoride.  —  Formula  CrF6.  —  Chromic 
per-fluoride  is  obtained  by  distilling  lead  chromate  with  cal- 
cium fluoride  (fluor  spar)  and  sulphuric  acid  : 


PbS04+  (CaS04)8+  (H,0),+  CrF. 

An  orange  vapor  is  evolved,  which  condenses  to  a  blood-red 
liquid,  boiling  at  a  temperature  but  little  above  that  of  the 
air,  fuming  in  contact  with  moist  air,  and  decomposed  by 
water,  forming  hydrofluoric  and  chromic  acids. 

CHROMIUM    AND    OXYGEN. 

376.  Chromic  Tri-oxide.—  Formula  CrvlO3.  —  Chromic 
tri-oxide  is  obtained  by  mixing  a  saturated  solution  of  potas- 
sium di-chromate  with  its  own  volume  of  strong  sulphuric 
acid.  On  cooling,  splendid  crimson  needles  of  the  tri-oxide 
crystallize  out,  which  may  be  dried  on  a  porous  tile.  It  is 
deliquescent  in  damp  air,  and  is  decomposed  by  a  heat  of 
250°.  It  is  a  powerful  oxidizing  agent  ;  alcohol  poured  on 
it  is  at  once  inflamed,  and  ammonia  gas  reduces  it  with 
incandescence. 


280  IXORGAXIC  CHEMISTRY. 

377.  Chromic  Acid.—  /•'••/•/// <//</  H,CrO4.— By  solution 
of  chromium  tri-oxide  in  water,  an  acid  liquid  is  obtained 
which  contains  chromic  acid,  but  which  is  decomposed  on 
evaporation,  yielding  only  chromic  tri-oxide  again.    The  salts 
of  chromic  acid,  called  chromates,  are  numerous  and  impor- 
tant.   The  ortho-chromates  of  bismuth,  B'",CrO6,  and  of  mer- 
cury, Hg"3CrO6,  the  mono-meta-chromate  of  lead,  Pb"aCrO5, 
the  di-meta-chromates  of  sodium,  Na,CrO4,  and  of  barium, 
Ba"CrO4,  and  the  di-chromate  of  potassium,  K,Cr,OT,  are  all 
well-known  compounds.     Potassium  di-chromate  is  used  in 
dyeing  and  in  calico-printing. 

378.  Perchromic  A.cifi..—Fonnula  H,l'r,O,.  ^). — By  the 
action  of  hydrogen  peroxide  upon  an  acid  solution  of  pota>- 
sium  chromate,  a  bright  blue  liquid  is  obtained  which  evolves 
oxygen  with  effervescence,  and  becomes  green.    By  agitation 
with  ether,  the  blue  substance  is  dissolved  ;  and  on  standing, 
it  forms  a  bright  blue  layer  upon  the  surface  of  the  liquid. 
This  reaction  is  a  delicate  test  for  hydrogen  peroxide  or  for 
a  chromate. 

379.  Chromic  Oxide. — Formula  Cr2O3. — Chromic  oxide 
may  be  produced  by  igniting  its  hydrate,  or  by  decomposing 
the  tri-oxide  or  a  di-chromate  by  combustibles.     By  passing 
chromyl  chloride  vapor  through  a  red-hot  tube,  rhombohe- 
dral  crystals  of  chromic  oxide  are  obtained,  greenish-black 
in  color,  having  a  specific  gravity  of  5  -21,  and  hard  enough 
to  scratch  glass.     It  is  generally  produced  in  the  form  of  an 
amorphous  bright  green  powder,  which  after  ignition  is  in- 
soluble in  acids.     It  is  used  to  color  bank-notes  green. 

Chromic  oxide  may  act  as  a  positive  or  a  negative  oxide, 
according  to  the  oxide  with  which  it  unites.  With  the 
strongly  negative  sulphuric  oxide,  for  example,  it  forms 
chromium  sulphate,  Cr,(SO4), ;  while  with  calcium  or  mag- 
nesium oxide,  compounds  called  calcium  or  magnesium  chro- 
mites,  CaCr.,O4,  or  MgCfkO|,  are  obtained.  The  best  known 
of  these  is  FeCr.O,,  ferrous  chromite,  or  native  chromic 


OCCURHK\CK  OF  MA\(i  AXKSE.  281 

iron.  Chromium  sulphate  exists  in  solution  in  two  different 
modifications,  one  green,  the  other  violet;  with  potassium 
sulphate  the  latter  yields  a  double  sulphate,  which,  crystal- 
lizing in  violet-red  regular  octahedrons  with  twelve  molecules 
of  water,  is  known  as  potassio-chromium  alum,  KCr(SO4).2, 
12  aq.  Ortho-chromic  hydrate,  H3CrO3,  2  aq.,  is  precipitated 
by  ammonium  hydrate  from  boiling  solutions  of  chromic- 
salts  ;  and  an  intermediate  di-chromic  hydrate,  H4Cr2O.,  is 
used  as  a  pigment  under  the  name  of  Pannetier's  green. 

380.  Chromous   Oxide.  —  Formula  Cr"O.  —  Chromous 
oxide  is  known  only  in  the  form  of  hydrate,  produced  by 
precipitating  chromous   chloride  by  potassium  hydrate.     It 
acts  as  a  basic  oxide,  yielding  chromous  salts. 

381.  Cliroinyl  Chloride.—  Formula  (CrO2)"Clr—  Chro- 
myl  chloride  is  prepared  by  distilling  a  mixture  of  sodium 
chloride  and  potassium  di-chromate  with  sulphuric  acid.     It 
is  a  blood-red  liquid,  having  a  specific  gravity  of  I'll,  and 
boiling  at  118°.     Its  relation  to  the  chromates  is  as  follows: 

r  n  1  OH  r  o  f  OH  rvn  1  OK  rvn  I  C1  r  n  J  C1 
CrO,|OH  Cr02|OK  CrO,  j  OR  CrO2  j  QK  CrO2 


Hydro-potcuffatvt        Potassium  Potassium  Chromyl 

Chromate.  '  eliminate.  chromate.         chloro-chromate.         chloride. 

Potassium  chloro-chromate   crystallizes  from  a  hot  solution 
of  potassium  di-chromate  in  hydrochloric  acid,  on  cooling. 

(  SUB-GROUP  B.) 
MANGANESE. 

Symbol  Mn.     Atomic  mass  54*8.     Valence  U,  III,  IV,  VI,  and 

VII. 

382.  History  and  Occurrence.  —  Manganese  was  dis- 
covered by  Scheele  and  Berg-mann  in  1774,  in  a  mineral 
known  as  braunstein.  Owing  to  its  being  confounded  with 
magnetic  iron,  this  mineral  had  received  the  Latin  name 
of  this  substance,  magnesia  nigra  ;  whence  the  name  mag- 


282  l\()h'<;.L\/<    CHEMISTRY. 

nesium  first  given  to  the  new  metal  obtained  from  it.  This 
name  was  afterward  changed  to  manganesium,  to  distinguish 
it  from  the  true  magnesium,  obtained  from  the  magnesia 
alba.  Manganese  occurs  somewhat  abundantly  in  nature, 
combined  principally  with  oxygen.  The  mineral  pyrolusite 
is  manganese  di-oxide  ;  hausmannite  is  manganoso-manganic 
oxide  ;  and  manganite  is  manganic  hydrate.  Manganese  sul- 
phide, arsenide,  carbonate,  and  silicate  are  also  known  as 
minerals. 

383.  Preparation  and  Properties. — Manganese  is  ob- 
tained by  reducing  its  oxide  by  charcoal  at  a  high  tempera- 
ture.    It  is  a  grayish-white,  hard  metal,  resembling  cast  iron, 
and  very  brittle.     It  is  feebly  magnetic  and  has  a  specific 
gravity  of  8.     It  oxidizes  readily  in  the  air,  and  dissolves 
easily  in  acids.     It  forms  a  remarkably  beautiful  alloy  with 
copper,  and  it  is  largely  used  in  the  Bessemer  steel  process, 
in  the  form  of  a  rich  alloy  with  iron,  called  spiegel-eisen. 

MANGANESE    AND    CHLORINE. 

384.  Manganic    Chloride.  —  Formula   MnCl.{.  —  Man- 
ganic  chloride   is  a  very  unstable    compound,   obtained  by 
dissolving    manganic    oxide   in  hydrochloric    acid  at  a  low 
temperature.     It  is  a  brown  liquid,  readily  evolving  chlo- 
rine and  becoming  manganous  chloride. 

385.  Maiig-anous  Chloride.  —  Formula  MnClr — Man- 
ganous  chloride,   obtained    by   heating    the   hydrated    com- 
pound, or  by  the  direct  action  of  chlorine  on  manganese,  is 
a  pale  rose-colored  deliquescent  mass,  which  dissolves  readily 
in  water,  forming  a  definite  hydrate.    The  same  hydrate  is 
formed  whenever  manganese  oxide  or  carbonate  is  dissolved 
in  hot  hydrochloric  acid. 

MANGANESE   AND    OXYGEN. 

386.  Manganic  Tri-oxide. — Formula  MnvlO:r — Neither 
manganic  tri-oxide  nor  its  corresponding  hydrate,  manganic 


283 

acid,  is  knowD  in  the  free  state.  Their  salts,  however,  called 
manganates,  are  well-known  compounds.  Potassium  manga- 
uate,  K2MnO,,  is  produced  whenever  manganese  compounds 
are  heated  with  potassium  hydrate  or  carbonate.  A  deep 
green  mass  results,  which,  dissolved  in  water  and  evaporated 
in  vacuo,  affords  dark  green  crystals,  isomorphous  with  po- 
tassium sulphate.  The  manganates  are  all  unstable,  passing 
readily  into  permanganates  and  depositing  manganese  di- 
oxide. 

387.  Permanganic  Oxide.  —  Formula  Mu2O7.  —  When 
sulphuric  acid  and  potassium  permanganate  are  mixed  to- 
gether, previously  cooled  to  a  low  temperature,  a  dark-col- 
ored oily  liquid  separates  which  is  supposed  to  have  this  com- 
position.    It  oxidizes  and  inflames  organic  substances,  and 
may  be  converted  into  violet-colored  vapors,  which  explode 
when  heated  rapidly. 

388.  Permanganic  Acid.—  Formula  HMnO4.  —  By  treat- 
ing barium  permanganate  with  sulphuric  acid  and  evaporat- 
ing the  solution  in  vacuo,  permanganic  acid  is  obtained  in 
the  form  of  brown  crystals.     It  is  deliquescent,  dissolves  in 
water  with  a  red  color,  and  decomposes  at  32°,  evolving 
oxygen.     Its  salts,  the  permanganates,  are  more  stable  than 
the  manganates.     Potassium  permanganate   is  prepared  by 
removing  a  portion  of  the  base    from   the  mauganate,  by 
passing  through  its  solution  a  current  of  chlorine  gas  : 

(K2Mn04)2  +  C12  =  (KC1),  +  (KMnO4)2 


The  color  of  the  liquid  changes  from  green  to  purple-red, 
and  on  evaporation  yields  dark  purple-red  ortho-rhombic 
crystals,  soluble  in  sixteen  times  their  weight  of  water,  and 
isomorphous  with  potassium  perchlorate.  Permanganates 
act  as  strongly  oxidizing  agents,  and  are  used  extensively 
as  disinfectants. 

389.  Manganic  Oxide.  —  Formula  Mn2O.r  —  Manganic 
oxide  is  produced  when  manganic   hydrate  or  manganese 


284  IXOItd.-lXIC  CHKMISTKY. 

di-oxide  is  heated  to  low  redness.  It  is  a  black  powder, 
uniting  with  strong  acids  to  form  salts.  Manganic  sulphate 
forms  an  alum  with  potassium  sulphate,  having  the  formula 
KMn(SOj2,  12  aq.  Manganic  hydrate,  HMnO.,,  exists  na- 
tive as  the  mineral  mauganite. 

390.  Manganese  I>i- oxide.  —  Formula  MulvO.,. — The 
di-oxide  of  manganese  occurs  native  as  the  mineral  pyrolu- 
site,  in  steel-gray  ortho-rhombic  prisms,  of  specific  gravity 
4-9.     It  is  produced  whenever  a  lower  oxide  is  heated  with 
free  access  of  air.     When  heated  it  gives  off  oxygen,  and  is 
extensively  used  in  the  arts  as  an  oxidizing  agent  at  high 
temperatures.     Heated  with  sulphuric  acid,  it  evolves  oxy- 
gen and  forms  manganous  sulphate ;  with  hydrochloric  acid 
it  evolves  chlorine.     With  basic  oxides,  nia.iiirane.se  di-oxide 
forms  manganites  such  as  OaMnO,  and  K.2Mu.2O5. 

391.  Manganous  Oxide.  —  Formula  Mn"O.  —  Manga- 
nous oxide  is  obtained  by  igniting  manganous  carbonate  or 
oxalate  in  an  atmosphere  of  hydrogen.     It  is  a  grayish-green 
powder,  which  has  been  obtained  crystallized  in  emerald- 
green  regular  octahedrons.     Its  hydrate  is  thrown  down  as  a 
white  precipitate  on  adding  a  solution  of  potassium  hydrate 
to  one  of  a  manganous  salt.     It  quickly  becomes  brown  on 
exposure  to  the  air.     Manganous  oxide  unites  directly  with 
negative  oxides  to  form  the  manganous  salts.     Manganous 
sulphate,  MnSO^,  manganous  carbonate,  MnCO.,,  and  man- 
ganous silicate,  MnSiO,,  are  examples.    They  all  have  a  deli- 
cate pink  color. 

(  SUB-GROUP  C.) 

§1.   IRON. 
Symbol  Fe.     Atomic  mm*  55 '88.     Valence  II,  III,  IV,  and-  VI. 

392.  History  and  Occurrence.  —  Iron  is  one  of  the 
most  important,  as  it  is  one  of  the  most  abundant,  of  metals. 
It  has  been  known  from  the  earliest  historic  times,  Tubal 


PREP AHA  TJOX  or  i no \ .  285 

Cain  being  an  artificer  in  this  metal.  Even  in  pre-historic 
times,  implements  made  of  it  seem  to  have  been  used.  It  is 
doubtful  whether  it  occurs  native ;  the  native  iron  found  on 
the  earth's  surface  containing  generally  nickel,  and  being 
of  meteoric  origin.  Its  ores,  however,  are  very  numerous. 
Among  these  may  be  mentioned  :  ferroso-ferric  oxide  or  mag- 
netite, Fe3O4 ;  ferric  oxide  or  hematite,  Fe.,O3 ;  ferric  hy- 
drate or  limonite,  H^Fe^;  and  ferrous  carbonate  or  siderite, 
FeCO.r  It  occurs  also  in  numerous  other  minerals,  and  in 
vegetables  and  animals. 

393.  Preparation  and  Properties. — On  the  large  scale 
in  the  arts,  iron  is  produced  either  from  the  native  oxide  or 
from  the  artificial  oxide  obtained  by  roasting  the  native  car- 
bonate or  hydrate.  Alternate  layers  of  the  ore,  of  the  fuel, 
and  of  limestone  are  placed  in  an  enormous  furnace,  shaped 
like  a  double  cone  interiorly,  and  forty  to  sixty  feet  in 
height;  whence  it  is  commonly  called  the  "high  furnace." 
A  powerful  blast  of  hot  air  enters  at  the  bottom,  and  the 
combustible  matter,  at  the  high  temperature  produced,  re- 
moves the  oxygen  from  the  ore,  thus  reducing  it  to  the  me- 
tallic state,  according  to  the  equation  : 

FeA  -f   C,  =  Fe,  +   (CO), 

The  limestone  unites  with  the  silica  and  other  impurities 
present,  forming  an  easily  fusible  silicate,  which  collects 
above  the  melted  iron  and  is-  drawn  off  as  slag.  After  the 
iron  is  reduced  to  the  metallic  state,  it  takes  up  more  carbon, 
becomes  fusible,  melts,  and  runs  down  to  the  bottom  of  the 
furnace,  accumulating  in  a  narrow  cylinder  called  the  cru- 
cible. When  this  is  full,  it  is  tapped  by  driving  in  the  clay 
plug  which  closes  the  opening,  and  the  melted  iron  runs 
down  a  suitable  channel  into  molds  made  in  the  sand  for 
its  reception.  The  manufacture  of  cast  iron  in  the  high-  or 
blast-furnace  is  a  continuous  operation ;  the  materials  are 
constantly  added  above,  the  slag  and  melted  iron  are  drawn 


off  from  below,  usually  twice  a  day ;  and  this  is  kept  up  until 
the  furnace  wears  out.  The  iron  thus  made  is  known  as  cast 
or  pig-iron.  Three  varieties  are  distinguished ;  white  pig-iron, 
which  is  hard,  brittle,  and  crystalline,  uniformly  brilliant  and 
white,  of  specific  gravity  7 '5,  and  readily  fusible;  gray  pig- 
iron,  which  is  granular  in  structure,  gray  in  color,  very  soft, 
of  specific  gravity  7*1,  and  difficult  of  fusion;  and  mottled 
pig-iron,  which  has  intermediate  properties,  but  is  stronger 
than  either.  The  gray  iron  has  generally  least  carbon,  its 
color  being  due  to  a  separation  of  a  part  of  this  carbon  as 
graphite  during  the  cooling.  Hence  the  same  metal  sud- 
denly cooled,  as  when  "chilled"  or  cast  in  iron  molds,  may 
be  hard  and  white;  and  when  cooled  slowly  in  sand,  be  soft 
and  gray.  White  iron,  especially  the  variety  known  as  spiegel- 
eisen,  which  contains  manganese,  contains  nearly  ()  per  cent 
of  carbon;  gray  iron  contains  from  2  to  5  per  cent. 

Iron  is  refined,  or  converted  into  wrought  iron,  by  burn- 
ing out  the  carbon  and  silicon,  as  well  as  the  impurities  sul- 
phur and  phosphorus.  This  is  effected  usually  by  the  process 
called  "  puddling"  or  "boiling."  The  pig-iron  is  piled  up 
on  the  floor  of  a  reverberatory  furnace,  in  contact  with  some 
of  the  pure  ores.  On  lighting  the  fire  it  melts,  and  is  con- 
tinually stirred  to  mix  it  thoroughly  with  the  oxide.  Gradu- 
ally the  carbon  and  silicon  are  oxidized,  the  former  escaping 
as  gaseous  carbon  monoxide,  the  latter  being  retained  as  sili- 
cate of  iron  in  the  slag ;  until  finally  the  iron  becomes  pasty 
and  adheres  together  in  spongy  masses.  These  are  collected 
into  balls  of  25  to  30  kilograms  weight,  and  compacted,  first 
by  working  between  powerful  jaws  called  squeezers,  and  then 
between  rollers,  by  which  the  slag  is  pressed  out,  and  the 
iron  is  made  into  "muck  bar."  The  puddled  bar  is  cut  into 
short  pieces,  made  into  bundles,  heated,  and  again  passed 
through  the  rolls ;  the  operation  being  repeated  until  the 
wrought  iron  is  sufficiently  pure.  By  this  process  the  carbon 
is  reduced  to  one  half  of  one  per  cent,  sometimes  to  even 


287 

less,  and  the  other  foreign  matters  to  mere  traces.  If  the 
iron  retain  phosphorus,  it  is  brittle  when  cold,  and  is  called 
' '  cold-short ;  "  if  it  contain  sulphur,  it  is  brittle  when  hot,  or 
"red-short."  The  iron  thus  obtained  is  bluish-gray  in  color, 
is  fibrous  in  structure,  and  has  a  specific  gravity  of  7 '3 
to  7-9. 

Pure  iron  may  be  prepared  from  the  best  commercial  vari- 
eties, piano-forte  wire  for  example,  by  fusing  them  with  pure 
iron  oxide,  beneath  a  layer  of  glass,  to  keep  out  the  air,  in  a 
clay  crucible.  It  is  brilliant  silver-white  in  color,  softer  than 
wrought  iron,  capable  of  receiving  a  high  polish,  strongly 
magnetic,  of  specific  gravity  7*8,  and  crystallizes  in  the  reg- 
ular system.  When  obtained  by  electrolysis  its  specific  grav- 
ity is  8'1.  Iron  is  also  prepared  for  pharmaceutical  uses  by 
reducing  its  oxide  by  hydrogen  at  a  red  heat.  It  is  then 
obtained  as  a  black  powder,  burning  when  heated  in- the  air. 
In  its  purest  commercial  form,  iron  has  a  tenacity  superior 
to  that  of  any  other  metal,  except  nickel  and  cobalt.  Its 
ductility  is  also  very  great,  and  when  heated  it  may  be  rolled 
into  sheets  scarcely  thicker  than  paper.  At  a  full  red  heat 
it  becomes  pasty  like  wax,  and  may  then  be  welded.  It  melts 
at  a  high  temperature,  probably  above  2000°. 

Steel  is  iron  which  contains  from  0'6  to  nearly  2'0  per 
cent  of  carbon.  It  is  therefore  intermediate  in  this  respect 
between  cast  and  wrought  iron.  Two  methods  are  in  use  for 
making  steel.  In  the  one,  the  wrought-iron  bar  is  heated 
with  charcoal,  and  thus  made  to  take  up  again  a  portion 
of  carbon;  in  the  other,  the  carbon  is  burned  out  from  the 
melted  cast  iron  by  a  powerful  current  of  air.  The  former 
is  known  as  the  process  of  cementation.  Fig.  96  represents 
a  cross-section  of  the  furnace  in  which  it  is  effected.  The 
iron  bars  are  packed  in  charcoal  in  the  fire-clay  chests  or 
boxes  shown  in  the  figure,  the  whole  covered  with  sand  to 
exclude  the  air,  and  heated  to  redness  for  from  seven  to  ten 
davs,  after  which  it  is  allowed  to  cool  down  slowlv.  The 


288 


bars  are  now  brittle,  covered  with  blisters,  and  are  easily 
fusible.  They  may  be  at  once  piled  together,  heated,  and 
rolled  into  bars  of  "  shear-steel ;  "  or  they  may  be  broken  in 
small  pieces,  melted  in  crucibles  of  fire-clay,  with  the  addi- 
tion of  a  little  manganese  di-oxide,  and  cast  into  ingots; 


Fig.  9fi.  fomentation  Furnace. 

these  ingots  are  afterward  heated  and  drawn  out  under  the 
hammer  into  bars.  In  this  form  it  is  known  as  "cast  steel." 
The  second  steel-process  is  named  the  Bessemer  process, 
from  its  inventor.  In  it  a  melted  cast  iron  rich  in  silicon 
is  run  directly  into  large  wrought-iron  vessels  lined  with  fire- 
clay, called  converters  (Fig. 
97),  where  this  iron  meets 
with  a  blast  of  air  blown  in 
under  a  pressure  of  two  en- 
tire atmospheres.  The  silicon 
in  the  iron  burns  vividly,  the 
air  at  the  high  temperature 
produced  acting  on  the  car- 
bon, sulphur,  and  other  impu- 
rities, to  oxidize  and  remove 
them.  At  the  end  of  about  twenty  minutes  the  luminous 
flame  suddenly  disappears,  and  a  malleable  iron  containing 
0'3  to  0*5  per  cent  of  carbon  is  left  melted  in  the  converter. 


Section.  Exterior. 

Fig.  97.  Bessemer  Converter. 


BESSEMER  STEEL  PROCESS.  289 

To  this  is  now  added  a  suitable  proportion  of  white  cast  iron 
— called  technically  spiegel-eisen — which  contains  manganese 
and  sufficient  carbon  to  convert  the  whole  into  steel.  It  is 
then  poured  into  molds,  and  the  ingots  thus  obtained  are 
hammered  or  rolled,  as  before.  Formerly,  attempts  were 
made  to  stop  the  air-blast  at  the  right  point ;  but  the  steel 
thus  made  varied  so  widely  in  quality,  that  the  process  above 
described  was  substituted.  Since  the  Bessemer  process  re- 
moves the  sulphur  only  partially,  and  the  phosphorus  not  at 
all,  it  is  evident  that  a  cast  iron  as  free  from  these  impu- 
rities as  possible-  must  be  employed.  By  simply  lining  the 
converter  with  a  mixture  of  clay,  silica,  lime,  and  magnesia, 
constituting  a  basic  material,  Thomas  and  Gilchrist,  in  1880, 
adapted  the  Bessemer  process  to  the  working  of  iron  con- 
taining a  notable  amount  of  phosphorus. 

Steel  resembles  iron  very  closely,  being  distinguished  from 
it  only  by  the  remarkable  property  it  possesses  of  being  ex- 
tremely hard  and  brittle  when  heated  and  suddenly  cooled. 
By  cautious  re-heating,  the  brittleness  thus  acquired  may  be 
diminished,  the  steel  becoming  highly  elastic  ;  this  process  is 
called  tempering.  For  the  manufacture  of  tools  and  cutting- 
instruments,  as  well  as  for  springs,  cementation  steel  is  pre- 
ferred;  but  for  many  other  purposes,  as  for  rails,  etc.,  Bes- 
semer steel  is  said  to  be  superior  to  it. 

Malleable  cast  iron  is  produced  by  heating  articles  made 
of  ordinary  white  cast  iron  to  redness  for  several  hours  in 
contact  with  an  iron  oxide.  A  reverse  cementation  process 
takes  place,  by  which  the  carbon  is  partially  removed  and 
the  iron  becomes  semi-malleable. 

IRON    AND    CHLORINE. 

394.  Ferric  Chloride.— Formula  FeCL,.— Ferric  chlo- 
ride has  been  found  native,  in  crevices  in  active  volcanoes. 
It  is  prepared  by  the  direct  action  of  chlorine  on  iron,  or  by 
heating  its  hydrate.  A  sublimate  of  iron-black  iridescent 


290  IXORGAXIC  CHEMISTET. 

scales  is  obtained,  which  have  a  metallic  luster,  and  are  vola- 
tile a  little  above  100°,  yielding  a  vapor  of  density  162'5. 
Ferric  chloride  is  deliquescent,  and  dissolves  in  water  with 
a  hissing  noise,  forming  a  hydrate.  This  hydrate  is  also  pro- 
duced by  dissolving  iron  in  hydrochloric  acid,  heating  the 
solution,  and  adding  nitric  acid  so  long  as  nitrous  gas  is 
evolved.  On  evaporation,  orange-red  rhombic  crystals  are 
deposited  having  the  composition  FeCl2,  3  aq. 

395.  Ferrous  Chloritle. — Formula  Fed.,. — When  chlo- 
rine or  hydrogen  chloride  gas  is  passed  over  iron  filings  in 
excess,  heated  to  redness,  ferrous   chloride   is   obtained  in 
white  shining  hexagonal  scales,  which  have  a  specific  gravity 
of  2*5,  and  are  deliquescent  in  moist  air.     Ferrous  chloride 
is  soluble  in  two  parts  of  water,  and  the  solution,  evaporated 
and  cooled  away  from  the  air,  deposits  bluish-green,  mono- 
clinic  crystals,  having  the  composition  FeCl2,  4  aq.    Ferrous, 
like  ferric  chloride,  forms  double  salts  with  alkali-chlorides. 

IRON    AND    OXYGEX. 

396.  Ferric  Tri-oxide.  —  Fvnnula  FevlO.,.—  Ferric  tri- 
oxide,  together  with  the  corresponding  ferric  acid,  are  both 
unknown.     Certain  salts  have,  however,  been  prepared  of 
analogous  constitution.     Such  is  potassium  ferrate,  produced 
by  projecting  iron  filings,  mixed  with  twice  their  weight  of 
niter,  into  a  red-hot  crucible.     On  extracting  the  mass  with 
ice-cold  water,  a  deep  cherry-red  solution  is  obtained,  which 
contains  potassium  ferrate,  crystallizing  in  dark  red  prisms. 
It  is  very  unstable,  being  easily  decomposed   into   oxygen, 
potassium  hydroxide,  and  ferric  oxide.     By  adding  barium 
chloride  to  this  solution,  a  purple-red  precipitate  of  barium 
ferrate   is  obtained,  which   is  far  more   stable.     It  has  the 
composition  BaFeO4,  aq. 

397.  Ferric  Oxidv.— Formula  Fe,'"Or—  This  oxide  of 
iron  occurs  abundantly  in  nature  in  two  forms :   one  crys- 
tallized in  rhombohedrons  and    mirror-like,  called   specular 


OXIDES  A XI)  HYDRATES  or  IROX.  291 

iron.;  the  other  columnar  or  fibrous,  sometimes  amorphous 
or  oolitic  in  structure  and  blood-red  in  color,  whence  it  is 
called  hematite.  Artificially,  it  may  be  obtained  in  rhombo- 
hedral  crystals  by  igniting  the  amorphous  oxide  in  a  slow 
current  of  hydrogen  chloride  gas  ;  and  as  an  amorphous  pow- 
der by  igniting  ferric  hydrate  or  ferrous  carbonate  or  oxalate. 
This  latter  variety  is  used  for  polishing  metals  and  glass, 
under  the  name  of  rouge,  crocus,  or  colcothar.  Its  specific 
gravity  is  about  5.  It  is  reduced  to  the  metallic  state  when 
heated  in  hydrogen.  After  ignition  it  is  almost  insoluble  in 
acids. 

398.  Ferric  Hydrates  exist  also  in  nature,  ortho-ferric 
hydrate,  H.^FeOy,  in  the  mineral  limnite,  di-ferric  hydrate, 
HjFcjjOg,  in  xanthosiderite,  and  meta-ferric  hydrate,  HFeO.,, 
in  gothite,  beside  other  and  intermediate  forms.    Ortho-ferric 
hydrate  is  precipitated,  on  adding  ammonium  hydrate  to  a 
solution  of  ferric  chloride,  as  a  bulky  brownish-red  precipi- 
tate, which  loses  water  upon  drying  and  forms  a  yellowish- 
brown  powder.     Moist  ferric  hydrate  forms  the  best  antidote 
in  cases  of  arsenical  poisoning.     It  is   used   also  in   calico- 
printing  as  a  mordant  and  in  purifying  gas. 

399.  Ferroso-ferric  Oxide.  —  ^Formula  Fe"Fe,'"O4.— 
This  oxide  of  iron  occurs  native  as  the  mineral  magnetite, 
crystallized   in   regular  octahedrons.     The   same  crystalline 
form  is  obtained  artificially  by  fusing  ferric  phosphate  with 
three  or  four  times  its  weight  of  sodium  sulphate.    This  oxide 
in  the  amorphous  form  is  produced  when  iron  is  heated  to 
redness  in  oxygen  or  steam.     It  forms  the  protecting  coating 
in  the  processes  of  Barff  and  Bower.     It  is  a  hard,  black,  me- 
tallic-like  solid,  of  specific  gravity  5*0,  and  highly  magnetic. 
It  is  one  of  the  most  valuable  of  iron  ores,  containing  72  per 
cent  of  this  metal.     Ferroso-ferric  oxide  may  be  regarded  as 
ferrous  ferrite,  derived  from  ferric  hydrate,  HFeO., ;  analo- 
gous to  ferrous  chromite,  Fe"GY./)r    Other  similar  compounds 
are   magnesium  ferrite,  Mg"Fe2O4,  known   as   the   mineral 


292  INOEGAXir  CHEMISTRY. 

magnesio-ferrite ;  and  zinc  ferrite,  Zn"Fe.,O4,  or  franklinite, 
in  which,  however,  a  part  of  the  zinc  is  replaced  by  iron  and 
manganese.  Ferroso-ferric  hydrate  is  precipitated  by  am- 
monic  hydrate  from  a  solution  containing  ferrous  and  ferric 
salts  in  suitable  proportions,  as  a  brownish-black,  dense  mass, 
which  dries  to  a  brittle,  strongly  magnetic  powder. 

4OO.  Ferrous  Oxide. — Formula  Fe"O. — Ferrous  oxide 
may  be  obtained  by  igniting  ferrous  oxalate  in  a  close  vessel, 
as  a  black  powder,  which  takes  fire  in  the  air  and  produces 
ferric  oxide.  Ferrous  hydrate  is  precipitated  whenever  solu- 
tions of  alkali-hydrates  are  added  to  solutions  of  pure  ferrous 
salts,  both  being  free  of  air.  White  flocks  are  thus  produced 
which,  dried  away  from  the  air,  have  but  a  slight  greenish 
tinge,  but  which  on  exposure  take  fire  and  burn  to  ferric 
oxide.  It  has  a  strong  reducing  action. 

Ferrous  oxide  forms  a  numerous  and  important  class  of 
salts.  United  to  sulphuric  oxide,  it  forms  ferrous  sulphate, 
FeSO4,  known  in  commerce  as  green  vitriol  or  copperas.  It 
is  produced  on  the  large  scale  by  exposing  ferrous  sulphide 
— obtained  by  roasting  ferric  di-sulphide,  or  pyrite — to  the 
weather,  by  which  it  is  oxidized : 

FeS  +  ((X),  =  Fe"SO4 
It  is  also  the  product  of  the   action  of  sulphuric  acid  on 

H2S04  -f  Fe  =  FeS04  -f  H2 

By  evaporating  its  solution,  pale  green  monocliuic  prisms 
crystallize  out,  having  the  formula  FeSO,,  7  aq.  The  same 
salt  occurs  native  as  the  mineral  melanterite.  The  crystals 
effloresce  in  dry  air,  and  lose  all  their  water  at  300°.  They 
are  soluble  in  one  and  a  half  parts  of  water  at  15°,  but  are 
insoluble  in  alcohol.  Both  the  crystals  and  their  solutions 
readily  oxidize  in  the  air.  When  heated  to  redness,  previ- 
ously perfectly  dried,  it  gives  off  sulphurous  and  sulphuric 
oxides,  leaving  a  pure  ferric  oxide.  It  is  therefore  used 
for  preparing  the  Nordhausen  or  di- sulphuric  acid.  It  is 


XICKEL  AND  COBALT.  293 

employed  in  the  arts  also  for  dyeing,  for  tanning,  and  for 
making  writing-ink. 

Ferrous  carbonate,  FeC03,  occurs  native  as  siderite,  or 
spathic-iron,  in  obtuse  rhombohedrons,  light  grayish-white  in 
color,  and  of  specific  gravity  3 '8.  It  is  throwrn  down,  on  the 
addition  of  a  soluble  carbonate  to  a  solution  of  a  ferrous 
salt,  as  a  white  precipitate,  rapidly  passing  into  brown  fer- 
ric hydrate  on  drying.  It  is  soluble  in  water  containing 
carbonic  acid ;  occurring  native  in  this  form  in  chalybeate 
springs. 

IRON    AND    SULPHUR. 

401.  Ferric  Di-sulphide.— Formula  FelvS2.—  This  sul- 
phide of  iron  occurs  native  in  two  forms ;  one  brass-yellow 
and  isometric,  called  pyrite ;  the  other  white  and  orthorhom- 
bic,  called  marcasite.     Buff  suggests  for  pyrite  the  formula 
S=Fe=S,  and  for  marcasite,  Fe=S=8.     Both  varieties,  on 
heating  in  close  vessels,  give  off  sulphur  and  yield  the  mag- 
netic sulphide,  Fe3S4. 

402.  Ferrous  Sulphide. — Formula  FeS. — Ferrous  sul- 
phide is  produced  by  the  direct  union  of  sulphur  and  iron, 
as  when  iron  wire  burns  in  sulphur  vapor,  or  when  the  two 
substances  are  melted  together  in  suitable  proportions.     It 
is  a  grayish-yellow  solid,  with  a  metallic  luster  and  crystal- 
line structure,  and  easily  fusible.     When  finely  divided  it  is 
oxidized  to  ferrous  sulphate  on  exposure  to  the  air.     With 
acids  it  evolves  hydrogen  sulphide  gas.     It  is  precipitated 
from  ferrous  solutions  by  alkaline  sulphides,  as  a  hydrate. 

§  2.  NICKEL  AND  COBALT. 

NICKEL. — Symbol  Ni.     Atomic  mass  58*56.     Valence  II,  III, 
and  IV. 

403.  History  and  Occurrence. — Nickel  is  one  of  the 
less  common   metals.      It  was  discovered  by  Cronstedt  in 
1751,  in  a  copper-colored  mineral,  to  which,  having  failed 

20 


294  1XORGAN1C  CHEM1STKY. 

in  attempting  to  extract  copper  from  it,  the  miners  had  ap- 
plied in  derision  the  name  kupfernickel.  From  this  mineral 
the  name  nickel  is  derived.  Nickel  occurs  free  in  nature 
only  in  meteoric  irons ;  in  combination  it  exists  in  many  min- 
erals, as  niccolite  (kupfernickel),  NiAs;  gersdorffite,  (NiS)".2 
A&jj  ullmannite,  Ni2S2(AsSb)2;  annabergite,  Ni3(AsO4)2;  zara- 
tite,  NiCO3,  with  nickel  hydrate;  and  rnorenosite,  NiSO4, 
7  aq. 

404.  Preparation  and  Properties. — Nickel  is  gener- 
ally obtained  commercially  either  from  kupfernickel  or  from 
an  artificial  arsenide  produced  in  the  manufacture  of  smalt, 
and  known  as  speiss.     These  arsenides  are  roasted  to  drive 
off  the  arsenic,  are  then  dissolved  in  hydrochloric  acid,  the 
antimony,  bismuth,  copper,  etc.  precipitated  as  sulphides  and 
removed,  the  iron  after  oxidation  precipitated  as  ferric  oxide 
by  ammonia,  the  ammoniacal  solution  exposed  to  the  air, 
and  the  nickel  thrown  down  by  potassium  hydroxide.     The 
dried  precipitate  is  formed  into  cubes  one  or  two  centimeters 
on  a  side,  mixed  with  pulverized  charcoal,  and  placed  in 
intensely  heated  fire-clay  cylinders.    The  nickel  oxide  is  re- 
duced, though  not  fused ;  the  small  tubes  of  metallic  nickel 
which  are  drawn  from  the  bottom  of  the  cylinders  being  sent 
in  this  form  into  commerce.     Nickel  is  a  pure  silver-white, 
ductile  and  malleable  metal,  of  specific  gravity  8 '6.     It  is 
exceedingly  infusible,  and  has  very  great  tenacity.     It  is 
magnetic,  but  loses  this  property  at  350°.     It  tarnishes  in 
moist  air,  oxidizes  readily  at  a  red  heat,  and  is  dissolved 
somewhat  slowly  by  acids.     It  is  largely  used  for  making 
German  silver,  which  is  an  alloy  of  nickel  with  copper  and 
zinc. 

COBALT. — Symbol  Co.     Atomic  mats  58*74.     Valence  II,  III, 
and  IV. 

405.  History  and  Occurrence. — The  property  of  cer- 
tain cobalt  compounds  to  color  glass  blue  was  known  to  the 


COMPOUNDS  OF  COBALT.  295 

ancient  Greeks  and  Romans.  Its  ores  were  long  known  to 
the  German  miners  under  the  name  of  cobalt,  a  term  derived 
from  kobold,  the  evil  spirit  of  the  mines,  who,  as  they  sup- 
posed, tantalizingly  offered  them  an  ore  rich  in  appearance, 
but  worthless.  The  metal  was  first  prepared  by  Brandt  in 
173Sf,  and  more  fully  studied  by  Bergmann  in  1780.  Co- 
balt occurs  in  nature  in  small  quantity  in  meteorites,  but 
principally  in  the  minerals  smaltite  or  speisscobalt,  cobaltite 
or  cobalt-glance,  erythrite  or  cobalt-bloom,  and  asbolite  or 
earthy  cobalt. 

406.  Preparation  and  Properties.  —  Cobalt  may  be 
obtained  by  reducing  its  oxide  —  obtained  from  the  arnmo- 
niacal  solution  mentioned  under  nickel — with  charcoal  or  in 
a  current  of  hydrogen.     It  may  also  be  obtained  by  igniting 
the  oxalate.     Cobalt  has  a  steel-gray  color,  with  a  tinge  of 
red ;  it  is  hard,  has  a  granular  fracture,  a  specific  gravity 
of  8'7  to  8*9,  and  is  malleable  at  a  red  heat.     It  takes  up 
carbon  and  becomes  fusible  in  an  ordinary  furnace.     It  is 
more  magnetic  than  nickel,  and  retains  its  magnetism  per- 
manently.   When  massive,  its  surface  becomes  tarnished  on 
exposure  to  moist  air.     It  oxidizes  readily  at  a  red  heat,  and 
burns  in  oxygen.     Sulphuric  and  hydrochloric  acids  dissolve 
it  slowly  with  the  evolution  of  hydrogen.     Nitric  acid  acts 
upon  it  readily. 

407.  Compounds  of  Cobalt. — Cobalt  forms  both  cobalt- 
ous  and  cobaltic  compounds.    Of  these,  cobaltous  chloride, 
CoCl.,,  a  blue  solid  which  forms  a  pink  hydrate — hence  used 
for  a  sympathetic    ink ;    cobaltous    nitrate,  Co"(NO3)2,  a 
rose-red  salt  used  as  a  blow-pipe  re-agent ;  cobaltous  sul- 
phate, CoSO4,  a  light-red  salt  crystallizing  with  seven  mole- 
cules of  water,  and  isomorphous  with  ferrous  sulphate ;  and 
cobaltic  oxide,  Co./"O3,  and  the  remarkable  cobaltamines, 
roseo-,  purpureo-,  xantho-,  and  luteo-cobalt,  may  here  be  men- 
tioned.     Smalt  is   an   impure  cobaltous   silicate,  made  by 
fusing  the  roasted  ore  with  potassium  carbonate  and  pulver- 


296  lyOUG  Ay  1C  CH  EM  IS  77,'  )  '. 


ized  quartz.  A  deep  blue  glass  is  thus  obtained,  which  is 
poured  into  water  and  thus  finely  divided,  in  which  state  it 
is  sent  into  commerce  as  a  pigment.  Zaffre  is  a  very  im- 
pure oxide  of  cobalt,  prepared  by  roasting  the  arsenical  ores 
and  mixing  the  product  with  twice  its  weight  of  sand.  It  is 
used  for  coloring  glass  blue.  Thenard's  blue  is  made*  by 
igniting  alumina  and  cobalt  phosphate  in  a  covered  cruci- 
ble. Rinrnan's  green  is  produced  by  treating  mixed  zinc 
and  cobaltous  oxides  in  the  same  way.  Both  are  used  as 
pigments. 

RELATIONS   OF   THE    GROUP. 

4O8.  The  periodic  law  requires  the  metals  of  this  group 
to  be  arranged  in  three  distinct  sub-groups.  In  the  first  is 
placed  chromium,  molybdenum,  tungsten,  and  uranium.  In 
the  second  is  placed  manganese,  and  in  the  third  is  placed 
iron,  nickel,  and  cobalt.  The  elements  of  the  first  sub-group 
have  a  striking  resemblance  in  properties  to  those  of  the  sul- 
phur group,  the  acid  oxides  CrOs,  MoO3,  WO.,,  and  UO,  cor- 
responding to  SO3,  SeO3,  and  TeO3  ;  their  salts  in  many  cases 
being  isomorphous.  In  the  second  group  manganese  resem- 
bles the  chlorine  group,  Mn.,O.  and  HMnO^  corresponding  to 
C1.2O7  and  H(J1O4,  the  permanganates  being  isomorphous  with 
the  perchlorates.  On  the  other  hand,  both  chromium  and 
manganese  show  strong  affinities  with  the  iron  sub-group, 
especially  on  their  basic  side  ;  the  acidic  character  being  most 
strongly  developed  in  chromium,  the  basic  character  in  iron. 
Moreover,  in  the  entire  group  there  is  an  odd  valence,  the 
valence  in  general  being  even.  The  vapor-density  on  the 
whole  does,  not  sustain  the  doubled  formula  M..C1,.. 


EXERCISES.  297 


EXERCISES.     . 
§1. 

1.  How  does  chromium  occur  in  nature?    Why  is  it  so  called? 

2.  What  valences  has  it  in  its  oxides?     Its  chlorides? 

3.  Write  the  graphic  formula  of  mercuric  ortho-chromate.     Of 
lead  mono-meta-chromate.     Of  barium  di-meta-chromate.     Of  potas- 
sium di-chromate.  , 

4.  By  the  following  reaction 

K.2Cr,0.  +  C2  =  Cr203  +  K2CO3  +  CO 
how  much  Cr203  will  a  kilogram  of  K.2Cr.,O7  yield  ? 

§2. 

5.  Write  the  reaction  in  preparing  manganese. 

6.  What  mass  of  potassium  permanganate  may  be  obtained  from 
a  kilogram  of  Mn0.2,  the  reaction  being: 

(MnO2)2  +  O3  -f  K,O  =  (KMn04)2? 

7.  Calculate  the  percentage  composition  of  manganous  silicate. 


8.  What  per  cent  of  iron  do  the  four  ores  mentioned  contain? 

9.  How  is  cast  iron  obtained  ?     What  are  its  varieties  ? 

10.  What  is  the  mass  of  a  cubic  dekameter  of  gray  iron? 

11.  What  are  the  chemical  changes  in  the  refining  of  iron? 

12.  Give  the  chemistry  of  the  two  processes  for  steel. 

13.  In  what  do  cast  iron,  wrought  iron,  and  steel  differ? 

14.  250  grams  pure  iron  are  burned  in  an  excess  of  chlorine.  What 
compound  is  formed?     What  mass  of  it? 

15.  Answer  the  above  questions,  using  oxygen  in  place  of  chlorine. 

16.  What  percentage  of  water  is  there  .in  the  mineral  gothite? 

17.  1,000  kilograms  pyrite  are  roasted  and  exposed  to  the  weather; 
what  mass  of  crystallized  ferrous  sulphate  may  be  obtained  by  its 
oxidation? 

18.  One  cubic  centimeter  of  spathic  iron  contains  what  volume  of 


298  INORGANIC  CHEMISTRY. 

§4. 

19.  What  percentage  of  nickel  does  iiiccolite  contain? 

20.  An  iron  vessel  weighs  156  grams;  what  will  be  its  mass  if  made 
of  nickel  ? 

21.  By  what  chemical  process  is  nickel  obtained? 

22.  The  mass  of  a  cube  of  cobalt  is  50  grams;  what  does  it  measure 
on  a  side? 

23.  What  mass  of  cobaltous  oxide  is  required  to  yield  36  grains  of 
cobaltous  nitrate?    Of  crystallized  sulphate? 


COPPER,  SILVER,  GOLD.  299 


CHAPTER    TENTH. 
COPPER,  SILVEK,  GOLD. 

§  1.   COPPER. 
Symbol  Cu.     Atomic  mass  63*4.     Valence  I  and  II. 

409.  History   and   Occurrence.  —  Copper   has   been 
known  from  the  earliest  times.     The  Romans  obtained  it 
from  the  island  of  Cyprus,  and   called  it  aes  cyprium,  a 
term  which  afterward  became  cuprum,  from  which  the  Eng- 
lish word  copper  is  derived.    Copper  is  found  abundantly  in 
nature  both  free  and  in  combination.     Native  copper  occurs 
in  masses  of  great  size  near  Kewenaw  Point,  Lake  Superior, 
one  of  which  weighed  over  400  tons.     The  workable  ores 
of  copper  are  the  oxides  cuprite  and  melaconite ;  the  sul- 
phides chalcocite,  covellite,  bornite,  and  chalcopyrite ;   the 
sulph-antimonite  tetrahedrite,  and  the  carbonates  malachite 
and  azurite. 

410.  Preparation  and  Properties. — The  method  ap- 
plied for  the  extraction  of  copper  varies  writh  the  ore  under 
treatment.     The  oxides   and  carbonates  are  simply  heated 
with  charcoal  or  other  fuel,  with  the.  addition  of  some  silice- 
ous flux.    The  sulphides  which  contain  iron  are  first  roasted, 
by  which  the  iron  sulphide  becomes  oxide,  and  some  copper 
oxide  is  produced.     The  mass  is  then  fused  with  silica,  thus 
forming  a  slag  containing  the  iron  as  silicate,  while  a  purer 
copper  sulphide  is  left.     By  repeating  this  roasting  and  the 
subsequent  fusion  several  times,  a  nearly  pure  copper  sul- 
phide is  obtained.     This  is  again  roasted,  the  copper  oxide 


300  L\OH(^  t  XI<  '  (  'JIKMISTR  V. 


now  produced  acting  upon  the  copper  sulphide  to  give  me- 
tallic copper,  thus  : 

Cu2S  +   (CuO)2  =  SO,  +  Cu4 

The  metal  is  refined  by  being  kept  melted  for  many  hours 
with  free  access  of  air.  The  more  oxidable  metals,  together 
with  some  copper,  pass  into  the  slag  as  oxides,  while  some 
of  the  copper  oxide  dissolves  in  the  melted  metal.  To  re- 
move this,  it  is  stirred  with  the  trunk  of  a  young  tree,  by 
which  this  oxide  is  reduced,  the  copper  becoming  at  the 
same  time  tough  and  fibrous.  If  this  "poling"  be  continued 
too  long,  the  metal  is  made  brittle  again.  Perfectly  pure 
copper  may  be  obtained  by  electro-deposition,  or  by  reducing 
the  oxide  by  a  current  of  hydrogen  gas. 

Copper  is  a  lustrous  metal,  flesh-red  in  color,  and  some- 
what softer  than  iron.  It  crystallizes  in  isometric  forms, 
has  a  specific  gravity  of  8*95,  and  conducts  heat  and  elec- 
tricity readily.  It  may  be  drawn  into  fine  wire  or  beaten 
into  thin  leaves.  Its  tenacity  is  considerable,  a  wire  two  mil- 
limeters in  diameter  sustaining  a  weight  of  140  kilograms. 
It  melts  at  about  1054°,  and  is  volatile  at  a  very  high  tem- 
perature. It  is  unaltered  in  ordinary  air  when  massive, 
though  when  finely  divided  it  often  takes  fire  spontaneously. 
When  heated  to  redness,  scales  of  oxide  form  on  its  surface. 
It  is  attacked  readily  by  chlorine  and  sulphur  and  by  nitric 
acid.  Weak  acids  and  alkalies  and  saline  solutions  act  on 
it  slowly  in  presence  of  the  air;  hence,  as  all  its  salts  are 
poisonous,  any  thing  to  be  taken  as  food  should  not  be  pre- 
pared in  vessels  made  of  this  metal  or  any  of  its  alloys. 

Copper  finds  extensive  use  in  the  arts,  both  as  such  and 
in  the  form  of  alloys.  The  alloys  of  copper  with  tin  and 
aluminum  have  been  mentioned.  With  zinc  it  forms  the 
well-knowTn  alloy  brass,  of  which  yellow-  or  sheathing-metal 
and  aich-metal  are  varieties.  Sterro-metal  is  a  brass  con- 
taining nearly  one  per  cent  of  tin  and  two  per  cent  of  iron. 


or  cor  PER.  301 

German  silver  is  an  alloy  of  copper,  zinc,  and  nickel.  Phos- 
phorus bronze  is  an  alloy  of  copper  and  tin  containing  nearly 
one  per  cent  of  phosphorus,  which  increases  its  hardness  and 
strength.  Silicon  bronze  contains  silicon  in  place  of  phos- 
phorus. 

COMPOUNDS   OF   COPPER. 

411.  Cvipric  Chloride,  Cud,,,  is  obtained  by  the  action 
of  chlorine  upon  copper,  or  by  drying  its  hydrate  at  200°. 
It  is  a  yellowish-brown  deliquescent  powder,  soluble  in  water, 
forming  a  green  solution  which  on  evaporation  deposits  crys- 
tals of  the  hydrate,  CuCl2,  2  aq.     It  forms  double  salts  wyith 

the  alkali-chlorides.     Cuprous  chloride,  Cu2012,  or   «  p  p,, 

is  formed  by  the  action  of  metallic  copper  upon  cupric  chlo- 
ride. On  pouring  the  solution  thus  obtained  into  water,  a 
dense  white  crystalline  precipitate  is  thrown  down,  which 
becomes  blue  on  exposure  to  air,  and  is  fusible  at  a  red  heat. 
Its  vapor-density  corresponds  to  the  formula  Cu2Cl2.  It  also 
forms  double  salts  with  the  chlorides  of  the  alkali-metals. 
A  cuprous  hydride,  CuH,  is  known. 

412.  Cupric  Oxide,  CuO,  occurs  native  as  melaconite. 
It  may  be  prepared  by  heating  the  metal  in  the  air,  or  by 
calcining  the  hydrate,  carbonate,  or  nitrate.     It  occurs  in 
isometric  forms — perhaps  also  in  orthorhombic — but  is  gen- 
erally massive.    Its  specific  gravity  is  6 "3,  and  it  fuses  with- 
out change  at  a  bright-red  heat.     It  is  easily  reduced  when 
heated  with  combustible  substances,  and  hence  is  used  in 
organic   analysis.      Cupric    hydrate,   Cu(OH)2,   is   thrown 
down  as  a  pale  blue  precipitate  on  adding  sodium  hydrate 
to  a  cold  solution  of  cupric  salt.     It  acts  strongly  basic,  and 
forms  numerous  salts.     Cupric  nitrate,  Cu(NO3)2,  is  pro- 
duced wrhen  copper  is  dissolved  in  nitric  acid.     On  evapora- 
tion, bright  blue  crystals  separate,  which  have  the  formula 
Cu(NO3)2,  3  aq.    Cupric  sulphate,  CuSO4,  commonly  known 
as  blue  vitriol,  is  obtained  by  dissolving  the  oxide,  carbonate, 


302  INOEGANIC  CHEMISTRY. 

or  hydrate  in  sulphuric  acid,  or  by  roasting  the  sulphide.  It 
crystallizes  with  five  molecules  of  water  in  triclinic  prisms, 
which  are  soluble  in  three  and  one  half  times  their  weight 
of  cold  water.  Cupric  ortho-phosphate,  liCu2PO5,  occurs 
native  as  the  mineral  libethenite.  Two  cupric  ortho-car- 
bonates occur  native :  malachite,  which  is  green,  Cu.2CO4, 
aq.,  and  azurite,  which  is  blue,  JI2Cu3(CO4)2.  Cuprous  ox- 
ide, Cu,2O,  forms  the  mineral  cuprite.  It  is  obtained  by 
reducing  a  solution  of  copper  with  grape-sugar  in  presence 
of  an  alkali-hydrate.  It  is  a  bright  red  powder,  isometric  in 
its  natural  forms,  and  of  specific  gravity  6'0.  Acids  decom- 
pose it  into  cupric  oxide  and  copper. 

413.  Cupric  Sulphide,  CuS,  is  found  native  as  the  min- 
eral covellite.     It  is  hexagonal  in  its  crystallization,  is  of  a 
bluish-black  color,  and  has  a  specific  gravity  of  4 '6.     It  is 
precipitated  from   cupric   solutions   by  hydrogen   sulphide. 
Cuprous   sulphide,  Cu2S,  also  occurs  native,  forming  the 
mineral  chalcocite.     It  is  produced  abundantly  in  smelting 
copper.     It  crystallizes  in  orthorhombic  prisms,  is  blackish 
lead-gray  in  color,  and  is  easily  fusible.     It  acts  as  a  sulphur 
base,  forming  cuprous  sulph-arseuites  and  autimonites. 

§  2.    SILVER. 
Symbol  Ag.     Atomic  mass  107 '66.     Valence  I  and  III. 

414.  History  and  Occurrence. — Silver  has  been  known 
in  the  metallic  form  from  the  earliest  historic  times.     It  oc- 
curs native,  both  crystallized  and  massive,  and  is  found  also 
in  combination,  as  sulphide,  in  argentite ;  as  sulph-antimo- 
nite,  in  pyrargyrite,  miargyrite,  and  stephanite ;  as  chloride 
in  cerargyrite ;  as  bromide  in  bromyrite ;  as  chloro-bromide 
in  embolite,  etc. 

415.  Preparation. — The  process  employed  for  the  ex- 
traction  of  silver  varies  with  the  quality  of  the  ore.     At 
Freiberg,  the  ore — an  impure  sulphide — is  roasted  with  ten 


PROPKH  77  /«>'  07^  S/L  VER.  303 

per  cent  of  salt,  the  resulting  mass  is  ground  to  a  fine  pow- 
der, and  agitated  in  revolving  barrels  containing  water  and 
scrap  iron,  by  which  the  silver  chloride  is  reduced  to  the 
metallic  state.  "Mercury  is  then  added  to  dissolve  the  silver, 
and  by  distilling  the  amalgam  thus  obtained  the  silver  is  left 
pure.  A  crude  modification  of  this  process  is  employed  in 
Mexico  and  Chili.  Much  of  the  lead  of  commerce  is  argen- 
tiferous. To  extract  the  silver  from  it,  the  lead  is  melted  in 
large  iron  pots,  and  allowed  to  cool  gradually.  Crystals  of 
pure  lead  separate,  while  the  alloy  of  silver  and  lead  remains 
fluid.  These  crystals  are  removed  and  re-melted,  and  again 
allowed  to  cool ;  so  that  ultimately,  by  a  continuation  of  the 
process,  a  very  rich  alloy  is  obtained,  which  may  contain  300 
ounces  of  silver  to  the  ton.  This  alloy  is  then  cupelled ;  i.  e.t 
it  is  melted  in  a  reverberatory  furnace,  whose  hearth  is  com- 
posed of  bone-ash,  and  the  lead  oxidized  by  allowing  a  cur- 
rent of  air  to  pass  over  it.  The  lead  oxide  thus  formed  fuses 
and  is  absorbed  by  the  bone-ash,  while  the  silver,  being  un- 
altered, is  finally  left  pure.  Native  copper  containing  silver 
is  separated  from  the  silver  by  electrolysis. 

416.  Properties. — Silver  is  a  remarkably  white,  brilliant 
metal,  of  specific  gravity  10 '5.  It  is  harder  than  gold,  but 
may  be  hammered  into  leaves  only  one  four-thousandth  of  a 
millimeter  thick,  and  drawn  into  wire  so  fine  that  two  thou- 
sand meters  wrould  weigh  but  one  gram.  It  has  a  high  tenac- 
ity, the  weight  of  85  kilograms  being  required  to  break  a 
wire  of  silver  two  millimeters  in  diameter.  It  is  the  best 
conductor  of  heat  and  electricity  knowrn.  It  is  fusible  at  • 
about  954°,  and  may  be  distilled  at  a  full  white  heat.  It 
may  be  obtained  in  isometric  crystals  by  slow  cooling.  When 
melted  it  is  capable  of  absorbing  twenty-two  times  its  vol- 
ume of  oxygen  gas,  which  is  again  evolved  when  it  solidifies. 
It  is  unaltered  in  the  air  at  any  temperature,  though  it  is 
readily  acted  on  by  chlorine,  by  sulphur,  and  by  phosphorus. 
Nitric  acid  dissolves  it  easily,  sulphuric  and  h/drochloric 


304  INORGANIC  CHEMISTRY. 

acids  with  difficulty.     It  is  not  attacked  by  melted  niter  nor 
by  fused  alkali-hydrates. 

417.  Uses. — Owing  to  its  softness,  silver  is  rarely  used 
alone.     It  is  generally  alloyed  with  copper,  which,  while  it 
increases  its  hardness,  scarcely  injures  its  color.     The  coin- 
alloy  of  the  United  States  and  France  contains  10  per  cent 
of  copper;  that  of  England,  7'5,  and  that  of  Germany  12-5 
per  cent.     The  silver  used  in  silver-plate  contains  usually 
from  70  to  95  per  cent  of  pure  silver. 

COMPOUNDS    OF    SILVER. 

418.  Silver  Chloride,  AgCl,  occurs  native  as  cerargyr- 
ite.     It  may  be  obtained  by  the  direct  union  of  silver  and 
chlorine,  or  by  precipitating  a  solution  of  silver  nitrate  by 
a  chloride.     A  white,  curdy  mass,  soluble  in  ammonium  hy- 
drate, but  insoluble   in  nitric  acid,  is  thrown  down,  which 
on  drying  becomes  a  white  powder.     When  heated  it  fuses, 
and  on  cooling  solidifies  to  a  crystalline,  translucent,  sectile 
mass  resembling  horn,  whence  the  name  horn-silver,  some- 
times applied  to  it.     It  has  a  specific  gravity  of  5*4,  crystal- 
lizes in  isometric  forms,  and  turns  black  on  exposure  to  light. 
For  this  latter  reason  it  is  used  in  photography. 

419.  Silver  Oxide,  Ag.,O,  is  usually  prepared  by  adding 
a  strong,  hot  solution  of  silver  nitrate  to  one  of  potassium 
hydroxide.    It  is  also  the  product  of  the  combustion  of  silver 
at  high  temperatures.     It  is  a  dark  brown  or  black  powder, 
of  specific  gravity  7 '2,  easily  decomposed  by  heat  and  par- 
tially by  light.     It  is  scarcely  soluble  in  water,  though  am- 
monia dissolves  it  readily,  the  solution  depositing  a  violently 
explosive  crystalline  compound,  probably  the  nitride,  Ag3N, 
upon  exposure  to  the  air.     Silver  hydrate,  Ag(OH),  is  a 
strong  base,  reacts   alkaline,  and  becomes   silver  oxide  on 
heating  to  60°.     Silver  nitrate,  AgNOs,  is  prepared  by  dis- 
solving silver  in  nitric  acid  and  evaporating  to  crystalliza- 
tion.    Transparent  orthorhombic  prisms  are  obtained,  which 


OCCURRENCE  AND  PROPERTIES  OF  COLD.  305 

are  soluble  in  their  own  weight  of  cold  water.  They  fuse  at 
a  moderate  heat,  and  at  a  higher  temperature  are  decom- 
posed. Silver  nitrate  blackens  in  presence  of  organic  mat- 
ter ;  it  is  used  therefore  as  a  hair-dye  and  for  indelible  ink. 
Cast  in  sticks,  it  is  employed  as  a  caustic  in  surgery.  Other 
salts  of  silver  are  the  sulphate,  Ag2SO4,  and  the  phosphate, 
Ag3PO4.  Silver  peroxide,  AgO,  is  obtained  by  electrolysis 
of  silver  solutions  and  by  the  action  of  ozone  upon  the  metal. 

§  3.   GOLD.    • 
Symbol  An.     Atomic  mat*  196 '7.     Valence  I  and  III. 

420.  Occurrence. — Gold  occurs  quite  widely  distributed 
in  nature,  though  in  small  quantity.     It  is  found  generally 
in  quartz  veins  intersecting   metamorphic  rocks  of  various 
ages,  and  in  the  alluvial  detritus  which  has  resulted  from 
the  disintegration  of  these  rocks.     To  extract  the  gold  from 
the  auriferous  quartz,  the  whole  is  finely  pulverized  and  then 
treated  with  mercury,  which  dissolves  the  gold.     By  pressing- 
out  the  excess  of  mercury  and  distilling  off  that  which  is  left 
in  the  solid  amalgam,  the  gold  is  obtained  pure.     The  yield 
of  the  United  States  gold-fields  in  1866  was  $86,000,000,  and 
that  of  Australia  $30,000,000.     The  largest  single  mass  was 
found  in  Ballarat,  Australia  ;  it  weighed  184f  pounds. 

421.  Properties. — Gold  is  a  soft,  orange-yellow  metal, 
of  specific  gravity  19'33,  and  very  brilliant.     It  is  very  duc- 
tile, and  so  malleable  that  it  may  be  beaten  into  leaves  only 
one  ten-thousandth  of  a  millimeter  thick.    These  gold  leaves 
transmit  green  light,  though  when  rendered  non-lustrous  by 
heat   this  light  is  ruby-red.     Gold  crystallizes  in  isometric 
forms,  conducts  heat  and  electricity  well,  and  fuses  at  1035°. 
It  is  unaltered  in  the  air,  and  is  not  attacked  by  any  single 
acid  or  alkali-hydrate,  though  solutions  which  contain  free 
chlorine,  like  aqua  regia,  dissolve  it  readily. 

Gold  is  used  both  for  jewelry  and  for  coinage.     Being  too 


306  l\()l{<i.l\ir  r ///•;.!/ /.s/V.T. 

soft  for  either  purpose  alone,  it  is  alloyed  with  either  copper 
or  silver,  the  mint-alloy  of  the  United  States  consisting  of 
nine  parts  of  gold  and  one  of  copper.  The  purity  of  gold 
for  jewelry  is  estimated  by  the  carat,  pure  gold  being  twenty- 
four  carats  fine ;  hence  an  alloy  of  eighteen  parts  gold  to  six 
of  silver  and  copper  is  said  to  be  eighteen  carats  fine.  Gold 
is  freed  from  copper  by  cupellation,  and  from  silver  by  quar- 
tation.  The  latter  process  consists  in  adding  silver  to  the 
alloy  until  the  gold  forms  one  quarter  part,  and  then  dis- 
solving out  the  silver  by  nitric  acid.  The  gold  is  left  pure. 

EXPERIMENT. — Prepare  a  dilute  solution  of  gold  by  adding  to  a 
liter  of  water  a  few  drops  of  a  rather  strong  solution  of  auric  chlo- 
ride; then  drop  into  it  one  or  two  fragments  of  phosphorus  of  the 
size  of  a  mustard-seed,  and  place  the  whole  in  the  sunlight.  Soon, 
often  in  the  course  of  a  few  hours,  the  water  will  have  a  distinct 
purplish  tint.  This  will  deepen  in  color  until  finally,  if  the  solution 
has  the  proper  strength,  a  beautiful  ruby-red  liquid  will  be  obtained. 
Faraday  proved  that  the  color  of  this  liquid  is  due  to  finely-divided 
metallic  gold;  so  finely  divided  indeed  that,  though  gold  is  one  of  the 
heaviest  of  metals,  it  does  not  settle  out  of  the  liquid  on  standing. 

COMPOUNDS   OF  GOLD. 

422.  Auric  Chloride.— Formula  AuCl:r— This  chloride 
is  produced  by  dissolving  gold  in  aqua  regia  and  -removing 
the  excess  of  hydrochloric  acid  by  evaporation  to  dryness. 
A  dark  red,  crystalline,  deliquescent  mass  is  obtained,  which 
is  freely  soluble  in  water,  in  alcohol,  and  in  ether.     It  forms 
yellow  double  chlorides  with  hydrogen,  sodium,  potassium, 
and  ammonium  chlorides.     Aurous  chloride,  AuCl,  is  ob- 
tained by  gently  heating  auric  chloride.     It  is  a  nearly  white 
mass,  permanent  in  the  air,  and  insoluble  in  water.    By  boil- 
ing water  it  is  decomposed  into  auric  chloride  and  metallic 
gold. 

423.  Auric  Oxide,  Au2Os,  is  obtained  as  a  dark  brown 
powder  by  digesting  magnesia  in  a  solution  of  auric  chlo- 
ride, decomposing  the  magnesium  aurate  by  nitric  acid,  and 


EXERCISES.  307 

drying  the  residue  at  100°.  It  is  decomposed  by  light  and 
heat,  and  unites  readily  with  positive  oxides  to  yield  aurates, 
having  the  general  formula  M'AuO,.  Ammonium  aurate, 
known  as  fulminating  gold,  is  violently  explosive.  In  potas- 
sio-auric  sulphite,  K3Au"'(SO3)3,  auric  oxide  is  basic  or  posi- 
tive. Aurous  oxide,  A\i2O,  is  a  greenish  powder ;  one  of 
its  salts,  sodio-aurous  thio-sulphate,  Na.5Au'(S2O3)2,  2  aq., 
is  used  in  photography. 


EXEKCISES. 

1.  What  mass  of  copper  may  be  obtained  from  1,000  kilograms  of 
meluconite?     Of  chalcocite?     Of  malachite? 

2.  Calculate  the  composition  of  crystallized  cupric  sulphate. 

3.  100  parts  of  silver  form  by  union  with  chlorine  132-84  parts  of 
silver  chloride;  what  is  the  atomic  mass  of  silver? 

4.  How  is  silver  extracted  from  argentiferous  lead  ? 

5.  How  much  silver  is  needed  to  make  250  grams  silver  nitrate? 

(5.  What  is  the  mass  of  gold  in  a  sphere  five  centimeters  in  diam- 
eter made  of  a  gold-copper  alloy,  the  alloy  being  twenty-one  carats 
fine? 

7.  Cak-ulate  the  percentage  of  gold  in  potassium  chlor-aurate. 


308  2SOEGAXIC  CHEMISTRY. 


CHAPTER   ELEVENTH. 

GALLIUM,  INDIUM,  AND  THALLIUM. 

§  1.  GALLIUM. 
Symbol  Ga.     Atomic  mass  69*9.     Valence  II  and  III. 

424.  History  and  Properties. — The  element  gallium 
was  discovered  in  1875  by  Lecoq  de  Boisbaudran,  in  a  zinc- 
blende  from  Pierrefitte.     Its  name  comes  from  Gallia,  the 
Latin  name  of  France.    When  separated  by  electrolysis  from 
a  solution  of  its  sulphate  it  is  a  bluish-white  metal,  having 
a  specific  gravity  of  5*9,  and  fusing  at  the  very  low  temper- 
ature of  30°.     It  remains  untarnished  in  the  air  at  ordinary 
temperatures,  and  does  not  decompose  water.     It  is  not  vol- 
atile up  to  a  red  heat.     Heated  in  oxygen,  it  oxidizes  only 
upon  the  surface.     It  dissolves  readily  in  hydrochloric  acid 
and  in  potassium  hydroxide,  with  evolution  of  hydrogen.     It 
has  two  characteristic  violet  lines  in  its  spectrum.    Two  chlo- 
rides are  known,  GaCL,  and  GaCl;!,  obtained  by  the  action  of 
chlorine  upon  the  metal.    Gallium  oxide,  Ga.,O,,  is  obtained 
by  igniting  the  nitrate.     The  nitrate,  Ga(NO3)3,  and  the 
sulphate,  Ga.2(8O4)3,  are  well-known  salts.     The  existence 
of  gallium  was  predicted  by  Mendeleeff  by  means  of  the 
periodic  series. 

§  2.  INDIUM. 

Symbol  In.     Atomic  mass  113*4.     Valence  II  and  III. 

425.  History,  Preparation,  and  Properties. — Indium 
was  discovered  in  the  Freiberg  zinc-blendes,  by  Reich  and 
Hichter,  in  1863.     They  observed  that  the  impure  zinc  chlo- 


OCCUPEEXCK  OF  THALLITM.  309 

ride,  obtained  by  dissolving  the  roasted  ore  in  hydrochloric 
acid,  contained  a  substance  whose  spectrum  consisted  of  two 
indigo-blue  lines,  one  of  which  was  very  brilliant  and  more 
refrangible  than  the  other.  Indium  is  a  soft,  malleable  metal, 
resembling  lead,  of  specific  gravity  7/2.  It  is  unaltered  in 
the  air,  and  leaves  a  gray  streak  on  paper.  At  a  temper- 
ature of  176°  it  melts,  and  burns  with  a  violet  light,  produc- 
ing the  oxide.  Hydrochloric  and  sulphuric  acids  dissolve 
it  readily.  Indium  oxide,  InO,  is  a  straw-yellow  powder, 
becoming  brown  on  heating,  and  easily  reducible  on  char- 
coal. Indium  hydrate,  In"(OH).2,  is  thrown  down,  as  a  white 
precipitate,  from  solutions  of  indium  by  alkali-hydrates.  In- 
dium sulphide,  InS,  is  a  dark  yellow  powder.  Indium 
chloride,  InCl.,,  is  procurable  as  a  white  crystalline  subli- 
mate, which  is  deliquescent.  Indium  sulphate,  In2(SO4)3, 
is  easily  obtained  by  dissolving  the  metal  in  sulphuric  acid. 

§  3.  THALLIUM. 
Symbol  Tl.     Atomic  mam  203*7.     Valence  I  and  III. 

426.  History  and  Occurrence. — Thallium  was  discov- 
ered in  1861  by  Crookes,  in  a  residue  left  after  the  distilla- 
tion of  selenium  from  a  lead-chamber  deposit  obtained  from 
a  sulphuric-acid  factory  in  the  Hartz  mountains.  This  resi- 
due colored  a  gas-flame  intensely  green,  and  gave  a  spectrum 
consisting  of  one  brilliant  green  line.  From  the  peculiar 
tint  of  this  line,  Crookes  named  the  metal  thallium,  from 
VUMOS,  a  green  shoot.  Thallium  was  independently  discov- 
ered by  Lamy  nearly  a  year  later. 

By  the  aid  of  the  spectroscope,  which  will  detect  one  four- 
thousandth  of  a  milligram  of  thallium,  this  element  has  been 
proved  to  be  widely  distributed  in  nature,  though  in  very 
minute  quantities.  The  rare  mineral  crookesite  is  a  selenide 
of  copper,  thallium,  and  silver,  and  contains  seventeen  per 
cent  of  thallium.  Various  specimens  of  iron  and  copper 

21 


310 

pyrites  contain  from  a  four-thousandth  to  a  hundred-thou- 
sandth of  their  volume  of  thallium.  It  occurs  also  in  zinc- 
blende,  in  certain  varieties  of  lepidolite,  and  in  the  saline 
residues  at  Nauheim. 

427.  Preparation  and  Properties. — Thallium  is  gen- 
erally obtained  from  the  dust  deposited  in  the  tubes  which 
in  sulphuric-acid  works  convey  the  sulphurous  oxide  from 
the  pyrites  burners  to  the  leaden  chambers.  This  is  extracted 
with  water,  and  the  thallium  is  thrown  down  from  this  solu- 
tion as  chloride.    This,  by  solution  in  sulphuric  acid,  gives 
the  sulphate ;  and  from  this  metallic  thallium  may  be  pre- 
cipitated by  zinc. 

Thallium  is  a  brilliant,  nearly  white  metal,  softer  than 
lead,  and  having  a  specific  gravity  of  11'8.  It  is  malleable, 
but  not  ductile,  owing  to  its  want  of  tenacity.  It  melts  at 
294°,  and  crystallizes  in  octahedrons.  It  tarnishes  rapidly 
in  air  and  burns  brilliantly  in  oxygen.  Nitric  acid  dissolves 
it  readily.  It  is  strongly  dia-maguetic. 

428.  Thallic  Chloride,  T1CL,  is  obtained  by  acting  on 
thallium  with  an  excess  of  chlorine.     It  forms  double  salts 
with  the  chlorides  of  the  alkali-metals.     Thallous  chloride, 
T1C1,  is  precipitated  from  thallous  solutions  by  chlorides.    It 
is  white  and  crystalline,  resembling  lead  chloride.    Thallic 
oxide,  T12O3,  is  a  dark  red  powder.    Thallous  oxide,  T12O, 
is  reddish-black  in  color,  and  dissolves  in  water,  forming  a 
hydrate.    With  acids  it  yields  salts,  thallous  sulphate  being 
T12(SO4).     Thallic   sulphate,  T1.2(SO4),,  forms  'double  sul- 
phates with  the  sulphates  of  the  alkali-metals ;  but,  unlike 
those  formed  similarly  by  gallium  and  indium  sulphates,  they 
are  not  true  alums,  and  have  a  different  crystalline  form. 


CADMIUM,  MERGUEY.  311 


CHAPTER  TWELFTH. 
ZINC,   CADMIUM,   MEKCUKY. 

§  1.   ZINC. 

Symbol  Zii.  Atomic  mass  64*9.  Valence  II.  Relative  density 
32*45.  Molecular  mass  64*9.  Molecular  volume  2.  The  mass 
of  one  liter  of  zinc-vapor  is  2*91  grams  (32*5  criths). 

429.  History  and  Occurrence. —  An  ore  of  zinc  was 
used  by  the  ancient  Greeks  in  the  manufacture  of  brass,  un- 
der the  name  xa3/j.ta,  a  word  said  to  be  derived  from  Cadmus, 
who  first  taught  them  its  use.     The  first  zinc  was  made  in 
Europe  in  the  eighteenth  century,  it  having  been  until  that 
time  imported  from  China.     The  name  zinc  was  given  by 
Paracelsus  in  the  sixteenth  century.     Under  the  name  cal- 
amine  —  a  corruption  of  cadmia  —  two  ores  of  zinc  are  now 
known :  one  a  silicate,  the  calamine  proper ;   the  other  a  car- 
bonate, now  called  smithsonite.     Zinc-blende  or  sphalerite, 
and  red  zinc-ore,  or  zincite,  are  also  well-known  minerals. 

430.  Preparation  and  Properties. — Zinc  is  extracted 
from  its  ores  by  first  roasting  them  in  a  reverberatory  fur- 
nace, and  then  distilling  them,  mixed  with  charcoal,  in  close 
iron  or  earthen  vessels.     By  the  action  of  the  charcoal  the 
oxygen   is  removed  from  the  zinc  oxide  which  constitutes 
the  roasted  ore,  and  the  zinc  thus  set  free,  being  volatile,  dis- 
tills over  into  suitable  receivers.     In  Silesia  this  distillation 
is  effected  in  peculiarly-shaped  muffles  of  fire-clay;   in  Bel- 
gium, in  earthen-ware  tubes ;  and  in  England,  in  fire-clay 
crucibles.     The  English  zinc-furnace  is  represented  in  Fig. 
99.     It  is  conical  in  shape,  and  contains  an  interior  dome, 


312 


IXOR G.I X If  ( 'HEM IS TR Y. 


within  which  six  crucibles  are  placed,  each  of  which  has  a 
hole  in  the  bottom,  through  which  an  iron  pipe  passes  to 
convey  away  the  zinc-vapor.  The  crucibles  are  charged  with 
the  mixture  of  roasted  ore  and  coke,  the  covers  are  cemented 
on,  and  they  are  gradually  raised 
to  bright  redness.  At  first  the 
carbon  monoxide  burns  at  the 
mouth  of  the  tube,  but  soon  the 
greenish-white  flame  of  zinc  ap- 
pears;  the  tube  is  then  length- 
ened, and  the  condensed  zinc  is 
collected  in  suitable  vessels 
placed  beneath.  It  is  afterward 
re-melted,  cast  into  ingots,  and 
sent  into  commerce  under  the 
name  of  spelter. 

Zinc  is  a  bluish-white,  highly 
crystalline  metal,  of  specific  grav- 
ity about  7-0.  It  is  hard  and  Fi^  "•  English  zinc-furnace. 
brittle  at  ordinary  temperatures,  and  also  at  200°;  but  be- 
tween 100°  and  150°  it  is  malleable  and  ductile,  and  may  be 
rolled  into  thin  sheets.  At  412°  it  melts,  and  at  1040°  it 
boils,  evolving  a  vapor  having  half  the  normal  density;  its 
molecule  is  therefore  mou-atomic.  Zinc  is  oxidized  readily 
by  exposure  to  moist  air.  When  strongly  heated  it  burns 
brilliantly,  producing  the  oxide.  It  is  acted  upon  by  dilute 
acids,  by  the  halogens,  and  by  alkali-hydrates. 

Zinc  is  used  largely  in  the  arts  as  sheet-zinc,  for  various 
purposes ;  it  forms  the  positive  element  of  most  voltaic  bat- 
teries. Its  alloys  are  highly  valuable ;  with  copper  it  forms 
brass;  with  copper  and  tin,  bronze  and  bell-metal,  and  with 
copper  and  nickel,  German  silver.  Iron  alloys  readily  with 
zinc  on  being  plunged  into  a  bath  of  the  melted  metal ;  the 
zinc  coating  protects  the  iron  by  a  galvanic  action,  whence 
iron  thus  treated  is  called  galvanized  iron. 


ZL\C  CHLOIUDK  AM)  OM /)!<;.  :>lo 

COMPOUNDS    OF    ZINC. 

431.  Zinc  Chloride,  ZnCl2,  may  be  obtained  either  by 
the  direct  action  of  chlorine  upon  zinc,  or  by  dissolving  zinc 
in  hydrochloric  acid  and  evaporating  the  solution.  It  is  a 
white  or  grayish -white,  translucent,  crystalline  substance, 
easily  fusible,  and  volatile  at  a  red  heat.  It  is  very  deli- 
quescent, and  dissolves  in  water,  forming  a  definite  hydrate, 
ZnCl2,  2  aq.,  which  crystallizes  in  octahedrons.  It  forms  defi- 
nite compounds  with  ammonia  and  with  alkali-chlorides.  It 
is  used  as  a  caustic  in  surgery,  and  in  solution  as  an  anti- 
septic, and,  with  ammonium  chloride,  as  a  soldering-fluid. 
It  is  also  a  powerful  de-hydrating  agent. 

482.  Zinc  Oxide,  ZnO,  occurs  native  as  red  zinc-ore  or 
zincite.     It  is  the  sole  product  of  the  combustion  of  zinc  in 
the  air,  and  is  made  commercially  by  conducting  zinc-vapor 
into  chambers  through  which  a  current  of  air  passes.     It  is 
a  white  powder,  unalterable  in  the  air,  becoming  transiently 
yellow  on  heating,  and  insoluble  in  water.     It  is  used  exten- 
sively as  a  pigment.     Zinc  hydrate,  Zn(OH)2,  is  obtained 
on  adding  an 'alkali-hydrate  to  a  solution  of  a  zinc-salt,  as  a 
white  gelatinous  mass,  similar  to  alumina,  but  soluble  in  am- 
monia.    It  is  strongly  basic,  forming  well-defined  salts  with 
acids.     Zinc  sulphate,  ZnSO4,  known  as  white  vitriol,  is  ob- 
tained by  oxidizing  the  sulphide,  or  by  dissolving  the  metal 
in  sulphuric  acid.     It  crystallizes,  with  seven  molecules  of 
water,  in  orthorhombic   prisms.     Zinc  carbonate,  ZnCO3, 
occurs  native  as  smith sonite  ;  it  is  the  principal  ore  of  zinc. 
Zinc  ortho-silicate,  Zn"2  SiO4,  occurs  native  as  willemite ; 
and  with  a  molecule  of  water,  Zn2SiO(,  aq.,  is  known  as 
calamine. 

483.  Zinc  Sulphide,  ZnS,  is  found  in  nature  in  iso- 
metric crystals,  forming  the  mineral  sphalerite  or  blende.    It 
is  generally  yellowish-brown  in  color,  has  a  resinous  luster, 
and  is  translucent.     It  is  precipitated  from  zinc-solutions  by 


814  IXOIHi.LMC  CIl 

alkali-sulphides  as  a  white  precipitate,  easily  soluble  in  acids. 
The  native  sulphide  is  easily  converted  into  the  sulphate  by 
roasting  it  with  free  access  of  air. 

§  2.  CADMIUM. 

Symbol  Cd.  Atomic  mass  111*7.  Valence  II.  Relative  density 
55 '8.  Molecular  mass  111 *7 '.  Molecular  volume  2. 

434.  History  and  Preparation.  —  Cadmium  was  dis- 
covered in  1817  by  Herrmann  and  also  by  Stromeyer ;  the 
latter  gave  it  the  name  cadmium  from  cadmia,  the  ancient 
name  of  zinc-ore.     Its  sulphide  is  found  native  as  greenock- 
ite.     It  occurs  as  an  impurity  in  commercial  zinc  ;  but  as  it 
is  more  volatile  than  zinc,  it  comes  over  in  the  first  products 
of  its  distillation ;  these  are  dissolved  in  acid,  and  the  cad- 
mium precipitated  by  zinc,  in  the  metallic  state. 

435.  Properties. — Cadmium  resembles  zinc,  but  is  whiter, 
heavier,  more  easily  fusible,  and  more  volatile  than  that  metal. 
Its  specific  gravity  is  8*7.    It  is  malleable  and  ductile  at  ordi- 
nary temperatures,  but  becomes  brittle  at  82°,  and  crackles 
when  bent,  like  tin.     It  melts  at  315°,  and*  crystallizes  in 
regular  octahedrons  on  cooling.     It  is  unalterable  in  the  air, 
but  at  a  red  heat  it  burns,  producing  bro\vn  fumes  of  oxide. 
Acids  act. upon  it  slowly.     Its  compounds  are  analogous  to 
those  of  zinc. 

§  3.   MERCURY. 

Symbol  Hg.  Atomic  mass  199 '8.  Valence  I  and  II.  Relative 
density  99*9.  Molecular  mass  199*8.  Molecular  volume  2. 
The  mass  of  one  liter  of  mercury-vapor  is  8*96  grams  (100 
criths). 

436.  History  and  Occurrence.  —  Mercury  has  been 
known  from  the  earliest  times ;    it  is  mentioned  by  Theo- 
phrastus  as  /(JTOS  Spyvptr;,  whence  the  Latin  argentum  vivum 
and  the  English  quicksilver.    The  name  mercury,  from  the 


.1X1)  niorKHTLKX  OF  MKltCi'I!}'.     315 


planet  of  that  name,  was  given  by  the  alchemists  to  all  vola- 
tile substances,  but  only  this  one  has  retained  it.  Mercury 
occurs  native  in  small  quantity  ;  but  the  chief  ore  of  mer- 
cury is  the  sulphide,  called  cinnabar,  which  is  found  princi- 
pally in  Idria  in  Austria,  Almaden  in  Spain,  and  New  Alma- 
den  in  California. 

437.  Preparation.  —  In  Austria  and  Spain  the  mercury 
is  obtained  by  roasting  the  ore,  and  carrying  the  volatile 
products  through  a  series  of  chambers,  or  of  long,  narrow 
pipes,  in  which  the  metal  is  condensed.     A  better  process  is 
to  distil  the  sulphide  with  lime  or  iron  scales  in  close  vessels. 

438.  Properties.  —  Mercury  is  a  brilliant,  silver-white 
metal,  of  specific  gravity  13  '59  at  0°.     At  ordinary  temper- 
atures it  is  a  coherent  liquid,  but  cooled  to  —  40°  it  solidifies 
to  a  malleable  tin-white  mass,  easily  sectile,  and  crystallizing 
in  regular  octahedrons.     It  is  slightly  volatile  even  at  15°. 
It  boils  at  350°,  yielding  a  colorless  vapor  of  specific  gravity 
6  '976.     Mercury  is  unalterable  in  the  air,  but  at  its  boiling 
point  it  slowly  absorbs  oxygen,  a  crystalline,  dark  red  oxide 
forming  on  the  surface.     Hydrochloric  and  dilute  sulphuric 
acids  do  not  attack  it,  but  boiling  strong  sulphuric  acid,  and 
even  dilute  nitric  acid,  dissolve  it  readily.     Chlorine  and 
sulphur  unite  directly  with  it. 

Mercury  is  used  in  the  arts  for  filling  thermometers  and 
barometers,  and  very  extensively  for  extracting  gold  and  sil- 
ver from  their  ores.  Its  alloys  with  other  metals  are  called 
amalgams.  Tin-amalgam  is  used  to  cover  mirrors. 

COMPOUNDS   OF   MERCURY. 

439.  Mercuric  Chloride.  —  Formula  HgCl2.  —  This  chlo- 
ride, often  called  corrosive  sublimate,  is  formed  when  mer- 
cury is  acted  upon  by  an  excess  of  chlorine.     It  is  usually 
prepared  by  subliming  a  mixture  of  mercuric  sulphate  and 

Salt:    Hg(S04)    +    (NaCl)8  =    Na.2(S04)    +    HgCl2 

Mercuric  sulphate.    Sodium  chloride.    Sodium  sulphate.    Mercuric  chloride. 


316  /.\Y>/,'r,j  v/r  CHEMISTRY. 

A  white,  semi-transparent,  crystalline. mass  is  thus  obtained, 
which  has  a  specific  gravity  of  5'43,  melts  at  265°,  and  boils 
at  295°,  yielding  a  vapor  of  normal  density.  The  critical 
pressure  for  the  solid  is  about  420  millimeters.  It  is  soluble 
in  sixteen  parts  of  cold  and  three  parts  of  hot  water ;  from 
the  latter  solution  it  crystallizes  on  cooling  in  long  white 
orthorhombic  prisms.  Its  solution  tastes  acrid,  nauseous,  and 
metallic,  and  reacts  acid.  It  is  an  energetic  corrosive  poison. 
It  coagulates  albumin,  forming  an  insoluble  compound  with 
it ;  whence  white  of  egg  is  the  best  antidote  for  it  in  cases  of 
poisoning.  For  this  reason  also  mercuric  chloride  has  been 
used  to  preserve  wood.  Its  solution  is  decomposed  by  many 
metals,  with  the  deposition  of  mercury.  Mercurous  chlo- 
ride, HgCl,  ordinarily  called  calomel,  is  precipitated  when- 
ever a  chloride  is  added  to  a  solution  of  a  mercurous  salt. 
It  occurs  native  in  tetragonal  crystals.  Commercially,  it  is 
prepared  by  subliming  a  mixture  of  mercuric  sulphate,  mer- 
cury, and  salt : 

Hg(S04)  +  Hg  +  (NaCl),  =  Na./SO4)  +  (HgCl)a 

The  heavy  white  powder  which  condenses  is  washed  with 
water  to  remove  any  mercuric  chloride.  It  is  not  soluble 
in  water,  though  chlorine-water  and  nitric  acid  dissolve  it  by 
converting  it  into  mercuric  chloride.  It  volatilizes  below  a 
red  heat,  yielding  four  volumes  of  vapor ;  being  decomposed 
into  mercuric  chloride  and  free  mercury,  each  of  which  occu- 
pies two  volumes ;  hence  the  vapor  of  calomel  turns  gold- 
leaf  white,  and  sublimed  calomel  always  contains  some  cor- 
rosive sublimate.  Calomel  is  gradually  decomposed  by  light, 
and  is  blackened  by  ammonium  hydroxide,  whence  its  name. 
44O.  Mercuric  Iodide,  HgI2,  is  precipitated  as  a  brill- 
iant scarlet  crystalline  powder,  on  adding  a  solution  of  po- 
tassium iodide  to  one  of  a  mercuric  salt.  The  crystals  are 
tetragonal  octahedrons ;  but  on  heating  to  200°  the  iodide 
is  volatilized  and  condenses  in  bright  yellow  orthorhombic 


MERCURIC  AM)  MKRCUKOUH  SALTS.  317 

plates,  which  on  cooling  pass  again  into  the  red  variety. 
This  substance  is  therefore  dimorphous,  the  two  forms  being 
probably  polymeric.  Cuprous-mercuric  iodide,  prepared 
by  adding  copper  sulphate  and  then  sulphurous  acid  to  a 
warm  solution  of  mercuric  iodide  in  potassium  iodide,  is  a 
brilliant  carmine-red  powder,  which  changes  to  a  deep  choco- 
late-brown on  heating  to  70°.  Upon  cooling  it  regains  its 
original  color.  Mercurous  iodide,  Hgl,  is  obtained  as  a 
yellowish -green  powder  by  precipitating  a  mercurous  salt 
with  potassium  iodide. 

EXPERIMENT. — Heat  a  little  mercuric  iodide  in  a  porcelain  cru- 
cible covered  with  a  watch-glass.  Yellow  crystals  will  be  deposited 
on  the  lower  surface  of  the  glass;  and  these,  when  cold,  will  change 
back  to  red  on  touching  them  with  a  needle,  the  red  color  spreading 
gradually  over  the  entire  mass. 

441.  Mercuric   Oxide.  —  Formula  HgO. — When   mer- 
cury is  heated  in  the  air  to  near  its  boiling  point,  red  scales 
of  mercuric  oxide,  commonly  known  as  red  precipitate,  col- 
lect upon  its  surface.     The  same  oxide  is  obtained  by  heat- 
ing mercuric  nitrate  until  no  more  nitrous  fumes  are  evolved. 
Mercuric  oxide  is  soluble  in  acids,  yielding  mercuric  salts. 
The  di-meta-nitrate,  Hg(NO3)2,  aq.,  and  the  acid  and  the 
normal  mono-meta-nitrates,  H2Hg2(NO4),,  aq.,  and  Hg.{ 
(NO4)2,  aq.,  are  well-known  compounds.    The  di-meta-sul- 
phate,  Hg(SO4),  is  decomposed  by  water,  forming  the  yellow 
ortho-sulphate,  Hg,(SO(i),   turpeth  mineral.      Mercurous 
oxide,  Hg.,O,  is  an  unstable  black  powder,  obtained  by  the 
action  of  alkali-hydrates  upon  calomel.     With  acids  it  forms 
mercurous  salts. 

442.  Mercuric   Sulphide,  HgS,   occurs  native  as  the 
mineral  cinnabar,  both  massive  and  in  rhombohedral  crys- 
tals.    It  is  made  artificially  by  direct  synthesis.     It  is  brill- 
iant red  in  color,  and  is  used  as  a  pigment  under  the  name 
of  vermilion.     Mercurous  sulphide,  Hg2S,  is  a  black  pcw- 
der  known  as  ethiops  mineral. 


818 

The  mercury  amides  are  very  numerous.  Mercuric 
chlor-amide,  Hg  j  Xj  2  ,  is  known  in  pharmacy  as  white 
precipitate. 

RELATIONS   OF  THE    GROUP. 

443.  The  metals  of  this  group  are  closely  related  in  many 
ways.  Their  molecules  in  the  gaseous  state  are  all  moi> 
atomic.  Their  specific  gravity  increases  with  the  atomic  muss, 
while  the  fusing  and  boiling  points  decrease.  The  heat  of 
formation  of  their  compounds  also  decreases  as  the  atomic 
mass  increases. 

Atomic  Fusing  Boiling  Specific             Heat  of 

mass.  point.  poittt.  grarli;/          formation. 

Zinc                  64-9            412°  1040°            -7-0  ZnO      86,400 

Cadmium        111-7             315°  765°             8-7  CdO      66,400 

Mercury         199-8  —40°  350°           13-6  HgO     30,600 

Both  zinc  and  cadmium  are  bivalent  only,  while  mercury  is 
apparently  univalent  also.  But  the  significance  of  molecular 
formulas  for  bodies  in  the  solid  state  being  uncertain,  the 
simpler  formula  is  provisionally  adopted. 


EXERCISER. 

1.  Smithsonito,  containing  75  per  cent  of  zinc  carbonate,  yields 
what  mass  of  zinc  to  the  kilogram? 

2.  500  kilograms  of  blende  when  roasted  yield  what  mass  of  crys- 
tallized zinc  sulphate? 

3.  One  cubic  centimeter  of  mercury  will  give  what  volume  of 
vapor? 

4.  How  much  mercuric  sulphate  and  how  much  salt  are  required 
to  give  one  kilogram  of  HgCl2?    Of  HgCl? 

5.  Calculate  the  percentage  composition  of  HgO.    Of  Hg.,O. 


319 


CHAPTER   THIRTEENTH. 

POSITIVE    DYADS. 

§  1.  MAGNESIUM. 
Symbol  Mg.     Atomic  mass  23*94.     Valence  II. 

444.  History  and  Occurrence. — Under  the  name  of 
magnesia  alba,  magnesium  carbonate  was  brought  into  Eu- 
rope early  in  the  eighteenth  century;  Black,  in  1755,  showed 
that  this  substance  contained  a  peculiar  earth.     The  metal 
was  prepared  first  by  Davy  in  1808,  and  in  a  purer  form 
by  Bussy  in  1830.     Bunsen  and  Matthiessen,  in  1852,  pre- 
pared it  by  electrolysis  of  the  fused  chloride ;  and  in  1857 
Deville  and  Caron  obtained  it  in  large  quantity  by  acting 
upon  the  chloride  with  sodium,  a  process  subsequently  im- 
proved by  Sonstadt.     Magnesium  occurs  abundantly  in  na- 
ture, but  always    in   combination.      Its  hydrate  forms  the 
mineral  brucite ;   its  carbonate,  magnesite ;  its  sulphate,  ep- 
somite ;  its  borate,  boracite;   its  fluo- phosphate,  wagnerite, 
etc.     Numerous   magnesian    silicates   are  also  known;    and 
the  double   carbonate  of  magnesium  and  calcium,  or  dolo- 
mite, exists  abundantly  as  magnesian  limestone.    Magnesium 
chloride    exists  in  many  natural  waters,   especially  in   sea- 
water. 

445.  Preparation   and   Properties.  —  Magnesium  is 
prepared  on  the  large  scale  by  heating  to  bright  redness  a 
mixture  of  six  parts  of  magnesium  chloride,  one  of  sodium 
chloride,  one  of  calcium  fluoride,  and  one  of  sodium,  in  a 
covered  crucible.    The  globules  of  magnesium  thus  obtained 
are  purified  by  distillation  in  an  atmosphere  of  hydrogen. 


320  I \OIMA\IC  r//AM//.S'77M'. 

Magnesium  is  a  silver-white,  brilliant  metal,  having  a  spe- 
cific gravity  of  1'75.  It  is  somewhat  malleable  and  ductile, 
but  is  not  very  tenacious.  It  melts  at  a  red  heat,  and  may 
be  obtained  crystallized  in  regular  octahedrons.  At  higher 
temperatures  it  is  volatile.  It  is  permanent  in  dry  air,  though 
it  oxidizes  readily  in  moist  air.  Heated  to  redness  it  takes 
fire  and  burns  with  a  dazzling  light,  very  rich  in  ultra-violet 
rays.  A  wire  0-297  millimeter  in  thickness  gives  a  light 
equal  to  that  of  74  stearin  candles,  five  of  which  weigli  a 
pound.  Acids  attack  it  with  ease,  and  it  unites  directly 
with  most  negative  elements,  including  nitrogen.  It  has 
been  used  of  late  years  as  a  source  of  light  in  photography, 

COMPOUNDS    OF    MAUNKSIUM. 

446.  Magnesium  Chloride,  MgCl.,,  is  best  prepared  by 
igniting  the  double  chloride  of  magnesium  and  ammonium  ; 
the  ammonium  chloride  is  thereby  driven  off,  and  the  mag- 
nesium chloride   is  left  as  a  white,  translucent,  crystalline 
mass,  readily  fusible,  and  somewhat  volatile.     It  is  deliques- 
cent and  dissolves   in  water,  forming  the  hydrate  MgCl,, 
6  aq.    The  mineral  carnallite  is  a  potassio-magnesium  chlo- 
ride, KMgCl3,  6  aq. 

447.  Magnesium  Oxide,  MgO,  commonly  called  mag- 
nesia, occurs  native  as  periclasite,  crystallized  in  isometric 
forms.     It  is  the  sole  product  of  the  combustion  of  magne- 
sium in  air,  and  is  left  whenever  its  carbonate,  hydrate,  or 
nitrate  is  ignited.     It  is  an  infusible,  insoluble,  bulky,  white 
powder,  which  gradually  unites  with  water  to  form  the  hy- 
drate.   Magnesium  hydrate,  Mg(OH),,  is  precipitated  from 
solutions  of  magnesium  salts  by  alkali-hydrates.    It  is  slightly 
soluble  in  water,  and  reacts  alkaline  to  test-papers.    It  occurs 
in  nature  as  brucite,  crystallized  in  rhombohedrons.     Mag- 
nesium sulphate,  MgSO4,  may  be  prepared  by  dissolving 
the  oxide,  hydrate,  or  carbonate  in  sulphuric  acid.     It  is  ob- 
vtained  commercially  either  from  sea-water,  from  dolomite — 


OCCVRRKXCE  OF  CALCFTM.  321 

a  ealciomagnesian  carbonate — or  from  serpentine,  which  is 
a  magnesium  silicate.  It  occurs  native  as  epsomite,  MgSO4, 
7  aq.,  and  is  found  also  in  the  waters  of  bitter  saline  springs, 
as  those  of  Epsom  in  England ;  whence  the  name  Epsom  salt 
applied  to  this  substance.  It  crystallizes  in  orthorhombic 
prisms,  containing  seven  molecules  of  crystal-water.  They 
dissolve  in  twice  their  weight  of  cold  water  at  0°.  Magne- 
sium carbonate,  MgCO3,  is  found  in  nature  as  the  mineral 
magnesite.  Magnesia  alba,  the  common  commercial  form  of 
this  substance,  is  obtained  by  precipitating  the  sulphate  with 
sodium  carbonate.  It  Is  a  light,  white  powder,  soluble  in 
acids,  even  the  carbonic,  and  having  the  composition  H4Mg4 
(CO  j,,  2  aq.  It  occurs  native  as  hydromagnesite. 

§  2.  CALCIUM. 
Symbol  Ca.     Atomic  mass  39  -91.     Valence  II  and  IV. 

448.  History  and  Occurrence.  —  Calcium  carbonate 
and  sulphate  were  known  to  the  ancients,  the  former  being- 
burned  into  lime  for  making  mortar.     It  is  from  the  Latin 
name  for  lime,  calx,  that  the  word  calcium  is  derived.    The 
metal  itself  was  obtained  in  an  impure  form  by  Davy  in 
1808 ;   and  in  1855  Matthiessen  prepared  it  pure  and  in 
considerable  quantity.     Calcium  is  one  of  the  most  abundant 
of  the  elements.     As  carbonate,  it  forms  the  mineral  calcite, 
and  the  rock-masses  known  as  limestone,  chalk,  and  marble. 
As  sulphate,  it  forms  vast  beds  of  gypsum ;  as  phosphate,  it 
occurs  as  apatite  ;  as  fluoride,  in  fluor  spar ;  and  as  silicate, 
it  is  found  in  numerous  minerals.     It  forms  an  important 
constituent  of  the  animal  skeleton,  whether  external  or  inter- 
nal, and  is  essential  to  vegetable  growth. 

449.  Preparation  and  Properties. — Calcium  may  be 
prepared  either  by  the  electrolysis  of  its  chloride,  previously 
mixed  with  two  thirds  its  weight  of  strontium  chloride,  and 
fused  in  a  porcelain  crucible ;  or  by  igniting  the  iodide  with 


322  IXORGAXIC  CHEMISTRY. 

sodium,  or  the  chloride  with  sodium  and  zinc,  in  a  closed 
vessel.  It  is  a  light  yellow,  brilliant  metal,  of  specific  grav- 
ity 1*57,  very  malleable  and  ductile,  and  about  as  hard  as 
gold.  It  is  permanent  in  dry  air,  but  is  oxidized  if  the  air 
be  moist.  At  a  red  heat  it  burns  vividly. 

COMPOUNDS    OF    CALCIUM. 

45O.  Calcium  Chloride,  CaCl.2,  is  produced  by  dissolv- 
ing the  oxide  or  carbonate  in  hydrochloric  acid,  and  in  many 
other  ways.  It  is  therefore  frequently  a  waste  product  in 
the  chemical  arts.  On  evaporating  its  solution  in  water, 
hexagonal  crystals  of  the  hydrate,  CaCl2,  6  aq.,  are  obtained, 
which  lose  two  molecules  of  water  when  dried  in  vacuo,  and 
the  whole  at  200°.  The  crystals  are  used  with  snow  as  a 
freezing  mixture  ;  in  it  a  thermometer  falls  to  —48*5°.  Cal- 
cium chloride  melts  at  a  full  red  heat ;  it  has  a  strong  attrac- 
tion for  water,  and  is  deliquescent ;  it  is  hence  used  for  drying 


451.  Calcium  Oxide,  CaO,  commonly  known  as  lime,  is 
always  prepared  on  the  large  scale  by  igniting  its  carbonate. 
This  operation  is  conducted  in  a  rather  rude  furnace  of  ma- 
sonry called  a  kiln  (Fig.  100),  built  usually  upon  the  side  of 
a  hill.  An  arch  of  the  limestone  is  first  thrown  across  just 
above  the  fire,  and  upon  this  the  charge  rests.  The  fuel 
employed  is  generally  wood,  and  the  fire  is  maintained  for 
three  or  four  days,  until  the  whole  mass  is  converted  into 
lime.  The  purer  the  limestone,  the  better  the  product.  Per- 
fectly pure  lime  is  obtained  by  igniting  crystallized  calcite. 

Calcium  oxide  is  a  white,  hard,  infusible  substance,  of  spe- 
cific gravity  2 '3  to  3.  When  moistened  with  water,  it  unites 
directly  with  it,  with  the  evolution  of  great  heat,  to  form  the 
hydrate.  This  process  is  called  slaking.  Calcium  hydrate, 
Ca(OH)2,  is  a  soft,  white,  bulky  powder,  soluble  in  530  times 
its  weight  of  cold  water,  forming  an  alkaline,  feebly  caustic 
liquid,  known  as  lime-water,  which  yields,  on  evaporation  in 


Pit  VTA  If.  /  TIOX  OF  C.  I  LCI  I  'M  OXIDK.  323 

vacuo,  hexagonal  prisms  of  the  hydrate.  It  absorbs  carbon 
ili-oxide  readily.  Calcium  sulphate,  CaSO4,  occurs  native 
us  anhydrite ;  and,  crystallized  with  two  molecules  of  water, 
as  selenite.  It  is  also  found  massive  as  gypsum.  It  is  pre- 
cipitated on  adding  a  sulphate  to  a  concentrated  solution 


Fig.  100.  Lime-kiln. 

of  a  calcium  salt.  By  heating  gypsum  to  110°,  it  parts  with 
water,  producing  what  is  called  plaster  of  Paris.  The  burned 
gypsum,  on  being  mixed  with  water,  again  unites  with  it  and 
"sets"  or  becomes  hard.  Hence  its  use  as  a  cement.  Cal- 
cium carbonate,  CaCO.,,  is  an  abundant  mineral.  It  is  di- 
morphous, being  orthorhombic  in  aragonite,  and  rhombohe- 
dral  in  calcite.  It  occurs  also  more  or  less  pure  as  marble, 
chalk,  and  limestone.  In  water  containing  carbonic  acid 
it  is  quite  soluble ;  such  waters  are  called  hard.  Calcium 
phosphate,  Ca3(PO4)2,  is  precipitated  from  a  solution  of  a 
calcium  salt  by  sodium  phosphate  in  excess.  It  occurs  as  a 
fhio-phosphate  in  the  mineral  apatite,  and  forms  the  chief 


324  INORGAXIC  CUKMTSTRY. 

constituent  of  the  bones  of  animals.  Two  acid  calcium  phos- 
phates, HCaPO,  and  H4Ca(PO4).,,  are  known,  the  former, 
with  2  aq.,  constituting  the  mineral  brushite. 

$  3.    STRONTIUM  AND  BARIUM. 
STRONTIUM. — Kymhol  Sr.  Atomic  mass  87*3.  Valence  II  and  IV. 

452.  History  and  Occurrence. — Strontium  was  distin- 
guished as  a  peculiar  substance  by  Hope  in  1792.    The  metal 
was  first  prepared  pure  by  Bunsen  and  Matthiessen  in  1855. 
It  occurs  in  nature  both  as  sulphate  or  celestite,  and  as  car- 
bonate or  strontianite.    From  the  latter  name,  which  is  taken 
from  that  of  Strontian,  in  Scotland,  where  the  mineral  was 
first  observed,  the  name  strontium  comes. 

453.  Preparation  and  Properties. — Metallic   stron- 
tium is  prepared  by  the  electrolysis  of  its  chloride.     It  is  a 
pale-yellow  metal,  of  specific  gravity  2%54,  harder  than  lead, 
melting  at  a  1'ed  heat,  and  burning  vividly  if  exposed  to  the 
air.     It  is  quite  permanent  in  dry  air,  but  decomposes  water 
readily,  evolving  hydrogen. 

COMPOUNDS    OF    STRONTIUM. 

454.  Strontium  Chloride,  SrCl.,,  is  obtained  as  a  hy- 
drate, SrCL,,  3  aq.,  by  dissolving  the  oxide  or  carbonate  in 
hydrochloric  acid.     On  evaporation,  deliquescent  crystals  are 
obtained,  which  lose  their  water  on  fusion,  leaving  a  color- 
less, glassy  mass,  soluble  in  water  and  in  alcohol. 

455.  Strontium  Oxide,  SrO,  is  generally  prepared  by 
igniting  the  nitrate.     It  is  a  grayish-white,  porous  mass,  is 
infusible,  and  unites   energetically  with  water  to   form  the 
hydrate.     Strontium  hydrate,  Sr(OH).,,  prepared  as  above, 
is  soluble  in  water,  forming  an   alkaline  liquid  which,  on 
evaporation,  deposits  crystals  of  Sr(OH)2,  8  aq.     Strontium 
nitrate,  Sr(NO.,)2,  is  employed  in  pyrotechny  for  producing 
a  crimson  fire.     Strontium  di-oxide,  Srlv(X,  is  precipitated 


HA  III  I'M  AM)  ITS  ('(>MI>or.\I)S.  325 

as  a  hydrate  by  adding  hydrogen  peroxide  to  a  solution  of 
strontium  hydrate. 

BARIUM. — Symbol  Ba.    Atomic  mass  136*9.   Valence  Hand  IV. 

456.  History  and  Occurrence. — Barium  was  first  rec- 
ognized as  a  new  element  by  Scheele  in  1774.     Davy,  in 
1808,  first  isolated  the  metal.     The  compounds  of  barium 
which  occur  native  are  the  sulphate,  or  barite,  and  the  car- 
bonate, or  witherite.     The  former  from  its  weight  was  for- 
merly called  heavy-spar ;  hence  the  name  barium,  from  /3«/>wr, 
heavy. 

457.  Preparation  and  Properties. — Barium,  obtained 
by  the  electrolysis  of  its  chloride,  is  a  yellow,  lustrous,  mal- 
leable metal,  of  specific  gravity  4*0,  which  decomposes  water 
rapidly. 

458.  Compounds  of  Barium. — Barium  chloride,  Ba 
C12,  is  usually  obtained  by  dissolving  the  carbonate  or  the 
sulphide — prepared  from  the  native  sulphate — in  hydrochlo- 
ric acid,  and  crystallizing.     Orthorhombic  crystals  separate, 
having  the  formula  BaCl2,  2  aq. ,  which  lose  all  their  water 
at  100°.     Barium  oxide,  BaO,  is  a  grayish-white,  infusible 
mass,  obtained  by  heating  the  nitrate  to  redness.    With  wa- 
ter it  slakes,  forming  a  hydrate,  Ba(OH),,  which  crystallizes 
from  a  hot  saturated  solution  with  8  aq.     Barium  nitrate, 
Ba(NCX)2,  is  used  in  the  green  fire  of  pyrotechny,  for  which, 
however,  the  chlorate,  Ba(ClO3)2,  is  to  be  preferred.     Ba- 
rium sulphate,  BaSO^,  occurs  native  as  barite;  when  heated 
with  charcoal,  it  is  reduced  to  barium  sulphide,  BaS.     Ba- 
rium di-oxide,  BalvO.2,  is  produced  by  heating  the  oxide  in 
a  stream  of  oxygen.     It  is  used  in  the  preparation  of  hydro- 
gen peroxide. 

EELATIONS    OF   THE    GROUP. 

459.  To  this  group  belong  also  the  elements  beryllium 
and  erbium.     Two   sub-groups  are   indicated  here,  the  one 
containing  beryllium  and  magnesium  (probably  erbium  also), 


326  I SOlid  A  M< '  <  'HKMISTli  Y. 

and  the  other  calcium,  strontium,  and  barium ;  the  affinities 
of  the  former  sub-group  being  rather  with  zinc  and  cadmium, 
while  those  of  the  latter  are  with  the  alkalies.  The  specific 
gravity  of  the  latter  sub-group  increases  with  the  atomic 
mass. 


EXERCISES. 

1.  To  yield  5  cubic  centimeters  of  magnesium  requires  how  much 
magnesite? 

2.  What  is  the  relative  length  of  two  bars  5  centimeters  in  diam- 
eter, one  of  platinum,  the  other  of  magnesium,  each  of  which  has  the 
mass  of  a  kilogram  ? 

3.  What  mass  does  limestone  lose  in  burning? 

4.  Compare  the  percentage  composition  of  anhydrite  and  selonite. 

5.  Which  contains  most  oxygen,  strontianite  or  witherite? 


POSITIVE  M  OX  ADS.  327 


CHAPTER   FOURTEENTH. 

POSITIVE    MONADS. 

§  1.  LITHIUM. 
Symbol  Li.     Atomic  mass  7 '01.     Valence  I. 

460.  History  and  Occurrence. — Lithium  oxide  was 
recognized  first  as  a  peculiar   substance  by  Arfvedson  in 
1817.     The  metal  was  first  prepared  pure  by  Bunsen  and 
Matthiessen  in  1855.     Lithium  is  a  rare  substance,  being 
found  principally  in  the  minerals  amblygonite,  spodumene, 
petalite,  lepidolite,  and  triphylite.     The  water  of  a  mineral 
spring    in   Cornwall    contains   the   chloride   in   considerable 
quantity.    Traces  of  lithium  have  been  detected  by  the  spec- 
troscope in  sea -water,  in  many  minerals,  in  tobacco-ashes, 
and  even  in  meteorites. 

461.  Preparation  and  Properties.  —  Lithium  is  best 
obtained  by  the  electrolysis  of  the  fused  chloride.     It  is  a 
brilliant,  silver-white  metal,  somewhat  softer  than  lead,  and 
remarkably  light,  having  a  specific  gravity  of  only  0'578. 
It  melts  at  180°,  and  burns  in  the  air  with  an  intense  white 
flame  when  more  strongly  heated.     It  tarnishes  in  the  air, 
and  decomposes  water,  evolving  hydrogen.     Its  compounds 
are  the  chloride,  LiCl,  a  deliquescent,  fusible,  and  volatile 
salt;  the  oxide,  Li,O,  and  hydroxide,  Li(OH),  the  latter  a 
caustic,  strongly  alkaline  substance ;  the  carbonate,  Li^CCX, 
the  sulphate,  Li,SO4,  and  the  phosphate,  Li3PO4,  all  of 
which  are  well-defined  salts.     Its  spectrum  is  characterized 
by  an  intense  crimson  line  of  wave-length  0 '0006705  milli- 
meter. 


1XOIHIA MC  ( 'HKMISTH  Y. 


§  2.  AMMONIUM. 
Symbol  Am.   Formula  (NH4).  Molecular  mass  18 '01.   Valence  I. 

462.  History. — The  salts  which  ammonia  forms  by  di- 
rect union  with  acids  have  a  remarkable  similarity  to  those 
formed  by  the  metals  of  this  group.     To  account  for  this 
resemblance,  Berzelius,  in  1816,  acting  upon  a  theory  of 
Ampere,  proposed  to  consider  these  salts  as  compounds  of 
ammonium,  a  monad  compound  radical,  (NVH4)',  capable 
of  acting  like  the  monad  elements  sodium  and  potassium. 
Being  unsaturated,  ammonium,  if  it  exist  free,  in  list  exist  as 
a  double  molecule,  N2H8.     Weyl,  by  condensing  ammonia 
gas  in  presence  of  sodium,  obtained  a  bright  blue  metallic- 
like  liquid,  which  he  assumed  to  be  sod-ammonium,  N.2H0Nar 
By  acting  upon  ammonium  chloride  with  this,  a  similar  blue 
liquid  was  obtained,  which  he  considered  to  be  free  ammo- 
nium.    Moreover,  when  mercury  containing  one  per  cent  of 
sodium  is  placed  in  a  saturated  solution  of  ammonium  chlo- 
ride, it  swells  prodigiously  in  bulk,  becoming  a  pasty  mass, 
like  butter.    This  is  the  so-called  ammonium  amalgam.    It 
rapidly  decomposes,  yielding  ammonia  and  hydrogen  gases. 

463.  Compounds  of  Ammonium. — Ammonium  chlo- 
ride, (NH4)C1,  found  native  as  sal-ammoniac,  is  prepared  on 
the  large  scale  from  the  ammoniacal  liquors  of  the  gas-works, 
by  adding  hydrochloric  acid,  crystallizing  out  the  crude  chlo,- 
ride,  and  purifying  by  sublimation.     It  is  thus  obtained  in 
white  fibrous  masses,  soluble  in  2*72  parts  of  water  at  18°, 
and  crystallizing  in  cubes  and  regular  octahedrons.     It  is 
completely  dissociated  into  NH3  and  HC1  at  350°.     Ammo- 
nium sulphate,  (NH4)2SO4,  is  also  obtained  from  gas-liquor. 
It  occurs  in  transparent,  orthorhombic  crystals,  isomorphous 
with  potassium  sulphate.     Ammonium  nitrate,  (NH4)NO3, 
is  prepared  by  neutralizing  nitric  acid  with  ammonium  hy- 
droxide, and  crystallizing.    It  is  used  for  making  hyponitrous 


PRKP.  \  RA  TION  A  M)  P  HOP  Kit  TIES  OF  SODIUM.       329 

oxide  gas.  Commercial  ammonium  carbonate  is  a  mix- 
ture of  acid  carbonate  and  carbarnate,  (H(NHjCO,)2  and 
(NH4)(NH2CO2).  On  exposure  to  air  the  carbamate  is  vola- 
tilized. 

§  3.    SODIUM. 

Symbol  Na.     Atomic  mass  23 '0.     Valence  I  and  III. 

464.  History  and  Occurrence. — Sodium  oxide  was  first 
clearly  distinguished  from  potassium  oxide  by  Duhamel  in 
1736.    The  metal  was  first  obtained  by  Davy  in  1807.     So- 
dium is  one  of  the  most  abundant  of  the  elements.    Its  chlo- 
ride, or  salt,  known  as  the  mineral  halite,  is  found  not  only 
in  immense  deposits  of  rock-salt,  but  also  in  enormous  quan- 
tities in  sea-water  and  the  water  of  saline  springs.     Sodium 
also  occurs  in  the  form  of  nitrate,  or  soda-niter;  of  borate, 
or  borax ;  of  carbonate,  or  trona ;  and  of  silicate,  in  albite, 
oligoclase,  sodalite,  etc.     It  is  found  in  marine  plants,  and 
is  essential  to  animal  life. 

465.  Preparation  and  Properties.  —  Sodium  is  pre- 
pared by  reducing  its  oxide  by  carbon  at  a  white  heat,  thus : 

Nap  -f  C  =  Na2  +  CO 

Practically,  thirty  kilograms  of  dry  sodium  carbonate,  thir- 
teen kilograms  of  charcoal,  and  three  kilograms  of  chalk  are 
intimately  mixed  together, 
calcined,  and  introduced  in- 
to iron  cylinders  heated  in  a 
reverberatory  furnace  (Fig. 
101).  At  a  bright  red  heat 
the  sodium  distills  over,  and 
is  collected  in  the  flat  receiv- 
er shown  in  the  figure.  To 
purify  it,  it  is  re-distilled,  Fig.l01  Sodium-furnace. 

melted    under    petroleum, 

and  cast  into  ingots,  which  are  preserved  under  naphtha. 
Ca'stner's  process  consists  in  reducing  sodium  hydrate  by 


330  IXORd A  XI< '  ( 'HEM IS TR  Y. 

heatiog  it  to  825°  with  an  intimate  mixture  of  finely  divided 
iron  and  carbon,  prepared  by  mixing  the  iron  with  molten 
pitch. 

Sodium  is  a  lustrous,  silver-white,  soft  metal,  of  specific 
gravity  0*98,  becoming  brittle  at  — 20°,  and  fusing  at  97°. 
It  crystallizes  in  tetragonal  octahedrons.  On  exposure  to 
air  it  rapidly  tarnishes,  and  if  thrown  on  water,  decomposes 
it  with  effervescence ;  if  it  be  prevented  from  moving,  or  if 
the  water  be  warm,  it  takes  fire,  burning  with  a  character- 
istic yellow  flame,  and  yielding  a  spectrum  consisting  of  a 
double  yellow  line  of  wave-length  0-0005892  millimeter.  It 
is  used  in  metallurgy  as  a  reducing  agent. 

COMPOUNDS    OF    SODIUM. 

466.  Sodium  Chloride,  NaCl,  may  be  formed  by  the 
direct  union  of  its  constituents,  as  by  burning  sodium   in 
chlorine  gas.     It  is  obtained  commercially,  either  by  mining 
it  directly,  in  which  form  it  is  known  as  rock-salt,  or  by  evap- 
orating the  water  of  saline  springs ;  producing  boiled  salt,  if 
artificial  heat  be  used,  or  solar  salt,  if  the  heat  be  natural. 
Large   quantities   of  salt  are  obtained   from  sea -water,  of 
which  it  constitutes  2'75  per  cent.     Sodium  chloride  is  a  col- 
orless, transparent  solid,  crystallizing  in  cubes,  and  having 
a  specific  gravity  of  2'15.     It  has  an  agreeable  saline  taste, 
is  deliquescent  in  moist  air,  and  is  soluble  in  three  times  its 
weight  of  water.     It  melts  at  776 °, 

467.  Sodium  Oxide,  Na.2O,  and  Hydroxide,  Na(OH). 
Sodium  oxide  may  be  obtained  by  the  combustion  of  the 
metal  in  air,  or  by  heating  the  hydroxide  with  sodium.    It  is 
a  white,  fusible  substance,  which  unites  directly  with  water  to 
form  the  hydroxide.     Sodium  hydroxide,  known  commonly 
as  caustic  soda,  is  made  in  the  pure  form  by  the  action  of 
sodium  upon  water.     Commercially,  it  is  prepared  by  the 
action  of  calcium  hydrate — milk  of  lime — upon  sodium  car- 
bonate.    The   clear  liquid  thus   obtained  is   evaporated  in 


SO  1>I  I  M  N  67, ril.  I TE  AND  CARBOSA  TE.  331 

vessels  of  iron  or  of  silver,  and  the  fused  mass  which  is  left 
is  poured  on  to  flat  plates  or  cast  into  sticks.  It  is  a  white, 
opaque,  brittle  solid,  of  specific  gravity  2  '00.  It  is  deliques- 
cent and  absorbs  carbon  di-oxide  from  the  air,  forming  the 
carbonate.  It  may  be  obtained  crystallized  in  monoclinic 
prisms,  having  the  composition  (NaOH)2,  7  aq.  Sodium 
peroxide,  Na2O2,  is  produced  by  heating  sodium  in  oxygen, 
as  a  white,  friable,  deliquescent  mass. 

468.  Sodium  Sulphate,  Na.,SO4,  is  obtained  abundantly 
commercially,  as  a  residue  in  many  chemical  processes,  as  in 
the  preparation  of  nitric  and  hydrochloric  acids.     It  is  also 
largely  produced   as  an   intermediate  product  in  the   soda 
manufacture.      It  occurs    native,   anhydrous  as  thenardite, 
and  hydrated  as  mirabilite.     It  crystallizes  from  solution  in 
large  colorless  monoclinic  prisms,  which  have  the  composi- 
tion Na.,SO4,  10  aq.,  and  which  are  efflorescent  in  dry  air, 
losing  all  their  water.     The  anhydrous  salt  is  soluble  in  two 
and  a  half  parts  of  water  at  100°.     The  acid  salt,  hydro- 
sodium  sulphate,  HNaSO4,  is  formed  by  adding  sulphuric 
acid  to  the  normal  sulphate. 

469.  Sodium  Carbonate,  Na.,CO.{,  was  formerly  extract- 
ed from  the  ashes  of  marine  plants.     It  has  been  produced 
in  immense   quantities  from  salt  by  a  process  proposed  by 
Leblanc.    This  process  consists,  1st,  in  treating  the  salt  with 
sulphuric  acid,  by  which  sodium  sulphate  is  produced;  and, 
2d,  in  heating  the  sodium  sulphate  with  coal  and  limestone 
in  a  reverberatory  furnace,  by  which  sodium  carbonate  and 
calcium  sulphide  are  obtained  in  the  form  of  a  black  mass 
called  black-ash.     This  is  extracted  with  water,  evaporated 
to   dryness,   calcined  with   sawdust,  and  brought  into  com- 
merce as  soda-ash.     By  solution  in  water  and  evaporation, 
sodium  carbonate  is  obtained   crystallized,  Na.,C(X,  10  aq. 
The  Solvay  or  ammonia  process,  by  which  at  present  nearly 
all  of  the  sodium  carbonate  of  commerce  is  made,  depends 
on  the  slight  solubility  of  hydro-sodium  carbonate  in  water. 


332  IX  ORGANIC  C 


Hence,  if  a  solution  of  hydro-ammonium  carbonate  be  added 
to  one  of  sodium  chloride, 

NaCl  +  H(NHJCO3  =  HNaCO3  -f  NH4C1 
hydro-sodium  carbonate  separates  and  is  converted  into  Na2 
CO3  by  heat.  The  NH4C1  is  treated  with  lime  or  magnesia, 
and  the  ammonia  thus  set  free  is  used  to  produce  more 
H(NH4)CO3  ;  and  so  the  process  becomes  continuous.  The 
crystals  are  efflorescent,  are  readily  soluble  in  water,  have 
an  alkaline  reaction  and  a  nauseous  taste.  The  acid  salt, 
hydro-sodium  carbonate,  BCNaCO,,  is  prepared  by  expos- 
ing crystals  of  the  normal  salt  to  carbon  di-oxide  gas. 

470.  Sodium  Nitrate,  NaNO,,  is  brought  from  Peru, 
where  it  occurs  native,  under  the  name  soda  saltpeter.     It 
crystallizes  in  rhombohedrons  and  is  deliquescent.     Normal 
sodium  phosphate,  Na3PO4,  is  unstable.   Hydro-di-sodium 
phosphate,  HNa.,PO4,  is  alkaline  in  its  reaction,  while  di- 
hydro-sodium  phosphate,  H,NaPQ4,  reacts  acid. 

S  4.  POTASSIUM. 
Symbol  K.     Atomic  mass  39'03.     Valence  I,  III,  and  V. 

471.  History  and  Occurrence.  —  The  lye  obtained  by 
leaching  the  ashes  of  land-plants  has  long  been  used  in  soap- 
making  ;   and  the  solid  product  of  the  evaporation  of  this 
lye  has  long  been  known  in  commerce  as  potashes,  from  its 
origin.    The  metal  potassium  was  first  obtained  by  Davy  in 
1807,  by  the  aid  of  electricity  ;  but  it  was  soon  after  pre- 
pared chemically  by  Gay-Lussac  and  Thenard.    Potassium 
occurs  somewhat  abundantly  in  nature,  but  always  in  com- 
bination.    In  the  mineral  kingdom  it  is  found  as  nitrate  or 
niter,  as  chloride  or  sylvite,  as  potassio-magnesium  chloride, 
or  carnallite,  and  as  sulphate,  or  aphthitalite.    It  exists  also 
in  orthoclase  and  in  muscovite,  and  in  the  waters  of  the 
ocean  and  mineral  springs.     Land-plants  contain  it  largely, 
and  it  is  essential  to  animal  life. 


POTASSIUM  AND  ITS  COMPOUNDS.  333 

472.  Preparation  and  Properties. — Potassium  is  now 
prepared  by  calcining  an  intimate  mixture  of  the  carbonate 
with  charcoal,  obtained  by  igniting  the  tartrate.    The  process 
is  quite  similar  to  that  described  for  sodium ;  but  owing  to 
the  tendency  of  the  metal  to  unite  directly  with  the  carbon 
monoxide  to  produce  a  dangerously  explosive  body,  it  is  far 
more   difficult.     Potassium  is  a  soft,  brilliant,  bluish-white 
metal,  of  specific  gravity  0*865,  becoming  brittle  at  0°,  and 
at  62*5°  melting  to  a  liquid  resembling  mercury.    From  this 
it  may  be  crystallized  in  tetragonal  octa- 
hedrons.   It  may  be  distilled  in  hydrogen, 

and  gives  a  green  vapor.  It  tarnishes  in- 
stantly in  the  air.  and  must  therefore  be 
preserved  under  naphtha.  Thrown  upon 
water,  it  at  once  decomposes  it,  evolving 
so  much  heat  that  the  hydrogen  set  free 
takes  fire  and  burns  with  a  characteristic 
violet  flame  (Fig.  102).  It  unites  actively  Fte- 102.  P< 
with  chlorine  and  with  sulphur.  Its  spec- 
trum is  characterized  by  two  sharply  defined  lines ;  one  in 
the  red,  of  wave-length  0*0007680  millimeter,  and  the  other 
in  the  violet,  of  wave-length  0*0004045  millimeter.  By  means 
of  this  spectrum  as  minute  a  quantity  of  potassium  as  one 
three-thousandth  of  a  milligram  may  be  detected  with  cer- 
tainty. 

COMPOUNDS    OF   POTASSIUM. 

473.  Potassium  Chloride,  KC1,  constitutes  the  mineral 
sylvite.     It  is  obtained  commercially  from  sea-water,  or  from 
an  abundant  mineral  of  the  Stassfurt  mines,  carnallite,  which 
is  a  potassio-magnesium  chloride.     It  is  a  transparent,  color- 
less solid,  which  crystallizes  in  cubes,  has  a  specific  gravity 
of  1*9,  and  tastes  like  common  salt.     It  decrepitates  when 
heated,  melts  at  a  red  heat,  and  is  volatile  at  higher  temper- 
atures. •  It  dissolves  in  about  three  times  its  weight  of  water 
at  15°,  producing  great  cold. 


334  INOK(;.\M<    CHEMISTRY. 

Potassium  iodide,  KI,  is  prepared  on  the  large  scale  l>y 
the  direct  action  of  iodine  upon  potassium  hydroxide : 

(U  +  (KOH)6  =  (KI;3  +  KI03  +  (H2O)3 

Iodine.         Potassium        Potassium       Potassium          Water, 
hydrate.  iodide.  iodate. 

By  evaporation  of  the  solution,  and  gentle  ignition  of  the 
residue,  the  iodate  is  converted  into  iodide.  Potassium  iodide 
occurs  in  cubical  crystals,  which  are  deliquescent  in  moist 
air.  It  is  readily  soluble  in  water  and  alcohol,  and  has  a 
specific  gravity  of  3.  Potassium  bromide,  KBr,  is  quite 
similar  in  properties  to  the  iodide,  and  is  obtained  by  an 
analogous  process. 

474.  Potassium  Oxide,  K,O,  and  Hydroxide,  K(OH). 
Potassium  oxide  is  obtained  by  the  direct  oxidation  of  potas- 
sium or  by  the  action  of  potassium  upon  the  hydroxide.     It 
is  a  white,  deliquescent,  and  caustic  substance,  which  unites 
energetically  with  water  to  form  the  hydroxide.    This  hydrox- 
ide, commonly  called  caustic  potash,  is  generally  prepared  by 
the  action  of  milk  of  lime — calcium  hydrate — on  potassium 
carbonate.     The  solution  may  be  evaporated,  and  the  fused 
hydroxide  thus  left  be  cast  into  sticks,  the  form  in  which  it  is 
usually  found  in  commerce.     It  is  a  white,  opaque,  deliques- 
cent, brittle  mass,  of  specific  gravity  2-1,  and  freely  soluble 
in  water  and  alcohol.     Its  solution  is  powerfully  alkaline, 
turning  reddened  litmus  back  again  to  blue,  neutralizing 
completely  the  strongest  acids,  and  acting  readily  upon  the 
skin.     In  the  solid  form  it  is  sometimes  used  as  a  cautery. 
Potassium  also  forms  a  di-oxide,  K.,O.(,  and  a  tetr-oxide, 

KA. 

475.  Potassium  Salts. — Potassium  chlorate,  KC1O.,, 
is  prepared  by  passing  chlorine  through  a  solution  of  potas- 
sium chloride  containing  milk  of  lime : 

KC1  -f  (Ca(OH),)s  +  (CU  =  (CaCl2)8  +  (H2O)3  -f  KC1O, 
By  evaporation  of  the  solution  the  chlorate  crystallizes  out. 


RUBIDIUM  AND  CJK8IUM.  335 

Potassium  sulphate,  K.2!SO4,  is  obtained  as  a  residue  in  the 
preparation  of  nitric  acid  from  niter,  and  is  a  product  also 
of  the  evaporation  of  sea-water.  It  forms  hard  orthorhom- 
bic  crystals,  which  have  a  bitter  taste,  and  dissolve  in  ten 
parts  of  cold  water.  Potassium  nitrate,  KNO2,  occurs  as 
an  efflorescence  upon  the  surface  of  the  soil  in  Bengal.  It 
is  extracted  by  solution  in  water,  and  evaporation,  and  is 
brought  into  commerce  as  crude  saltpeter.  It  is  also  ob- 
tained by  decomposing  native  sodium  nitrate,  or  native  or 
artificial  calcium  nitrate  by  potassium  carbonate.  It  crys- 
tallizes generally  in  transparent  orthorhombic  prisms,  which 
are  not  deliquescent,  have  a  cooling  taste,  and  dissolve  read- 
ily in  water.  It  fuses  below  redness  to  a  colorless  liquid, 
and  at  a  high  temperature  is  decomposed,  evolving  oxygen. 
It  deflagrates  with  combustibles,  and  is  used  in  making  gun- 
powder. Potassium  carbonate,  K2CO3,  is  the  essential  con- 
stituent of  the  crude  potash  of  commerce,  which  is  obtained 
by  evaporating  the  teachings  of  wood-ashes.  When  refined 
it  is  known  as  pearlash.  It  forms  a  white,  granular,  very 
deliquescent  mass,  having  an  alkaline  reaction,  and  fusible 
at  full  redness.  It  is  soluble  in  less  than  its  own  weight  of 
water,  but  is  insoluble  in  alcohol.  The  acid  salt,  hydro- 
potassium  carbonate,  HKCO:i,  is  permanent  in  the  air, 
and  has  a  faintly  alkaline  reaction. 

§  5.  •  RUBIDIUM  AND  CAESIUM. 
RUBIDIUM. — Symbol  Rb.     Atomic  mass  85*2.     Valence  I. 

476.  Preparation  and  Properties.  —  Rubidium  was 
first  detected  in  the  water  of  the  Durckheim  mineral  spring, 
by  Bunsen,  in  1860,  by  means  of  the  spectroscope.  Its  spec- 
trum contains  two  characteristic  dark  red  lines;  hence  its 
name,  from  the  Latin  rubidus,  dark  red.  By  distilling  the 
carbonate  with  charcoal,  rubidium  is  obtained  as  a  soft  white 
metal,  of  specific  gravity  1-5.  It  melts  at38'5°,  and  vola- 


336  INORGANIC  CHEMIST  U  Y. 

tilizes  below  a  red  heat.  It  is  more  easily  oxidized  than 
potassium,  and  takes  fire  in  the  air,  burning-  with  a  violet 
flame. 

477.  Rubidium  Salts. — The  salts  of  rubidium  resemble 
very  closely  those  of  potassium.     The  chloride  crystallizes 
in  cubes,  dissolves  in  its  own  weight  of  water  at  150°,  and 
forms  a  double  salt  with  platinum  chloride.     The  nitrate, 
RbNCX,   resembles    saltpeter,  but  crystallizes   in  hexagonal 
prisms.    The  carbonate,  Rb2CO3,  is  an  alkaline  deliquescent 
salt.    The  sulphate,  Rb.2SO4,  is  isomorphous  with  potassium 
sulphate. 

CAESIUM. — Symbol  Cs.     Atomic  mass  132'7.     Valence  I. 

478.  History. — Caesium  was  discovered  at  the  same  time 
with  rubidium,  and  in  the  same  mineral  water.     The  name 
caesium  comes  from  caesius,  sky-blue,  and  has  reference  to 
two  bright  blue  lines  in  its  spectrum.    The  Diirckheim  water 
contains  in  five  kilograms  scarcely  one  milligram  of  caesium 
chloride ;  but  the  lepidolite  of  Hebron,  in  Maine,  contains 
0*3  per  cent  of  caesium,  and  the  rare  mineral  pollucite  con- 
tains 32  per  cent.     Metallic  caesium  was  obtained  by  Setter- 
berg,  in  1882,  by  electrolysing  a  mixture  of  four  parts  of 
caesium  cyanide  and  one  part  of  barium  cyanide.     It  is  a 
soft  metal,  as  white  in  color  as  silver,  has  a  specific  gravity 
of  1*88,  and  fuses  between  26°  and  27°,  passing  through  the 
pasty  state.    The  salts  of  caesium  resemble  those  of  rubidium. 


337 


EXERCISES. 

1.  Give  the  theory  of  ammonium.     Illustrate  it. 

2.  What  volume  of  ammonia  gas  in  one  kilogram  of  (NH4).2SO4? 

3.  Twenty  kilograms  Na2CO3  yield  how  many  cubic  centimeters 
of  sodium? 

4.  One  cubic  centimeter  rock-salt  contains  what  mass  of  sodium? 
What  volume  of  chlorine? 

5.  Write  the  reactions  in  the  soda-process  of  Leblanc. 

6.  One  hundred  kilograms  of  salt  yield  what  mass  of  sodium  car- 
bonate? 

7.  By  decomposing  a  kilogram  of  NaNO3  by  K2CO3  what  mass 
of  KNO3  is  obtained  ? 

8.  How  much  water  will  one  gram  of  potassium  decompose?    One 
gram  of  sodium? 

9.  Bv  whom  were  rubidium  and  caesium  discovered?    When? 


APPENDIX. 


TABLE  L— THE  METRIC  SYSTEM. 


MEASURES  OF  LENGTH. 


Millimeter 

Centimeter 

Decimeter 

METER 

Dekameter 

Hectometer 

Kilometer 


0-001  of  a  meter, 
0-01       U 


0-1 
1 

10 
100 

1000 


meter, 

meters, 


Mvriameter  10000 


0-0394  incli. 
0-3937      M 
3-9370  inches. 
39-3704      " 
393-7043      " 
328  feet,  1  inch. 

3280  «    10  inches 

6-21 37  miles. 


MEASURES  OF  SURFACE. 

Cen tare  1  square  meter,  1550  square  inches 

ARE  100  square  meters,  119-6  square  yards. 

Hectare     10000  square  meters,  2-471  acres. 


Milliliter 

Centiliter 

Deciliter 

LITER 

Dekaliter 

Hectoliter 


MEASURES  OF  VOLUME. 
0-001  of  a  liter  (1  cu.  cm.)  0-0610  cubic  inch. 


0-01  »       " 

0-1  «       " 

1  cubic  decimeter, 

10  cubic  decimeters, 
100 


Kiloliter  (stere)  1000 


0-338    fluid  ounce. 

0-1056  quart. 
61-0271  cubic  inches. 

2-6417  gallons  (U.  S.) 
26-417 
264-17 


MASSES. 

Milligram 

0-001 

ms.     1 

cu.  mm.  water,       0-0154 

grain 

Av. 

Centigram 

0-01 

"     10 

"      " 

0-1543 

" 

M 

Decigram 

0-1 

"       0 

1  cu.  cm. 

1-5432 

grains 

" 

GRAM 

1 

"     1 

cu.  cm. 

15-4323 

" 

« 

Dekagram 

10 

"     10 

u        « 

0-3527 

ounce 

« 

Hectogram 

100 

"     1 

deciliter 

3-5274 

ounces 

" 

Kilogram 

1000 

"     1 

liter 

2-2046 

pounds 

« 

Myriagram 

1  0000 

"     10 

liters 

22-0462 

« 

« 

Quintal 

100000 

"     1 

hectoliter 

220-4621 

" 

" 

Tonneau 

1000000 

"     1 

cu.  meter     '      2204-6212 

" 

" 

(339) 

340 


A  PPEXDIX—  TA  JiLE  II. 


COMPARISON  OF  CENTIGRADE  AND  FAHRENHEIT  DEGREES. 


(Tut.     Fain: 

Cent.    Fain: 

Cait.    Fain: 

('cut.    Fahr. 

_40   —40-0 

—5   +23-0 

+  30   +86-0 

+  65  +149-0 

39    38-2 

4     24-8 

31     87-8 

66    150-8 

38    36-4 

3     26-6 

32     89-6 

67    152-6 

37    34-6 

2    28-4 

33     91-4 

68    154-4 

36     32-8 

—1     30-2 

34     93-2 

69    156-2 

35     31-0 

0     32-0 

35     95-0 

70    158-0 

34     29-2 

+  1     33-8 

36     96-8 

71    159-8 

33    27-4 

2     35-6 

37     98-6 

72    161-6 

32    25-6 

3     37-4 

38    100-4 

73    163-4 

31    23-8 

4     39-2 

39    102-2 

74    165-2 

30    22-0 

5     31-0 

40    104-0 

75    167-0 

29     20-2 

6    42-8 

41    105-8 

76    168-8 

28    18-4 

7    44-6 

42    107-6 

77    170-6 

27    16-6 

8    46-4 

43    109-4 

78    172-4 

26    14-8 

9    48-2 

44    111-2 

79    174-2 

25    13-0 

10    50-0 

45    113-0 

80    176-0 

24    11-2 

11     51-8 

46    114-8 

81    177-8 

23     9-4 

12    53-6 

47    116-6 

82    179-6 

22     7-6 

13     55-4 

48    118-4 

83    181-4 

21     5-8 

14    57-2 

49    120-2 

84    183-2 

20     4-0 

15     59-0 

50    122-0 

85    185-0 

19     2-2 

Hi    CO-8 

51    123-8 

86    186-8 

18   —0-4 

17    62-6 

52    125-6 

87    188-6 

17    +1-4 

18    64-4 

63    127-4 

88    190-4 

16     3-2 

19    66-2 

54    129-2 

89    192-2 

15     5-0 

20     68-0 

55    131-0 

90    194-0 

14     6-8 

21     69-8 

56    132-8 

91    195-8 

13     8-6 

22    71-6 

57    134-6 

92    197-6 

12    10-4 

23    73-4 

58    136-4 

93    199-4 

11    ll>-2 

24    75-2 

59    138-2 

94    201-2 

10    14-0 

25    77-0 

60    140-0 

95    203-0 

9    15-8 

26    78-8 

61    141-8 

96    204-8 

8    1.7-6 

27    80-6 

62    143-6 

97    206-6 

7    19-4 

28    82-4 

63    145-4 

98    208-4 

—6   +21-2 

+29   +84-2 

+64  +147-2 

99    210-2 

+100  +212-0 

-fllO  +230 

+210  +410 

+310  +590 

+410  +770 

120    248 

220    428 

320    608 

420    788 

130    266 

230    446 

330    626 

430    806 

140    284 

240    464 

340    644 

440    824 

150    302 

250    482 

350    662 

450    842 

160    320 

260    500 

360    680 

4(iO    860 

170    338 

270    518 

370    698 

470    878 

180    356 

280    536 

380    716 

480    890 

190    374 

290    554 

390    734 

490    914 

+290  +392 

+300  +572 

+400    752 

+  500  +932 

+500  4932 

+800  +1472   +1100  +2012 

+1400  +2552 

600   1112 

900   1652     1200   2192 

1500   2732 

+  700  -1-1292 

+  1000  +1832   1+1300  +2372 

+1600  +2912 

APPENDIX—TABLE  III. 


341 


3  • 

I 


l! 

§/o 

*"*^     O* 

I?. 

S'  3' 


T: 


Platiuic. 

Auric. 

Mercuric. 

Mercurous. 

Lead. 

Arsenic. 

Antimonic. 

Stannic. 

Stannous. 

Silver. 

Bismuth. 

Cupric. 

Cadmium. 

Ferric. 

Aluminum. 

Chromic. 

Cobalt. 

Nickel. 

Manganous. 

Zinc. 

Barium. 

Strontium. 

Calcium. 

Magnesium. 

Sodium. 

Ammonium 

Potassium. 

Hydrogen. 


23 


342 


APPENDIX— TABLE  IV. 


CQ 

w 

£ 
< 

fc 

hH- 
«! 

EH 


!11g11'i<5gSl>3.S!§i^I5.9    Sla-S(g4F«ir    SSsSf-g 


pS  c  *>  e 

e  0  c^s  w  j-     KJ  ^  c  o 

att^lz-Z-Zs-a 
3!ssfi28S?3l 

^^oooqo^oe;^^^ 


9  j   <D  s  •  «• 


I  s 


I  3 

j  g  sSSSSSSS  Si  ?Si5lS  8 


INDEX. 


Acetylene 232 

critical  temp,  of  .  7 

Acid,  antimonic  .  .  .217 
antimonous  .  .  .  217 

arsenic 213 

arsenous 215 

bismuthic  .  .  .  .  220 

boric 258 

bromic 148 

carbonic 240 

chloric 147 

chlorous  ....  146 

chromic 280 

di-phosphoric  .  208 
di-sulphuric  ...  168 
di-thionic  ....  170 

ferric 290 

hydrazoic  ....  189 
hydrobromic  .  .  .  120 
hydrochloric  ...  112 
hydrofluoric  .  .  .  121 
hydriodic  .  .  .  ,  121 
hydrosulphuric  .  154 
hypobromous  .  .  148 
hypochlorous  .  .  145 
hypoiodous  ...  149 
hyponitrous  ...  199 
hyposulphurous  .  157 

iodic 149 

manganic  ....  283 
meta-phosphoric  209 
meta-stannic  .  .  .266 

nitric 190 

nitrous 194 

ortho-stannic  .  .  266 
penta-thionic  .  .  170 
perbromic  ....  148 
perchloric  ....  148 
perchromic  .  .  .280 

periodic 149 

permanganic ...  232 
phosphoric  .  .  .  206 
pyrophosphoric  .  208 

silicic 254 

stannic 266 

sulph-antimonic  .  217 
sulpho-carbonic  .  249 
sulpho-sulphuric  170 
sulphuric  .  .  .  162 
sulphurous  .  .  159 
tetra-thionic  .  .  170 
thio-sulphuric  .  170 
tri-thionic  .  .  .170 

Acid  hydrogen  .   .       .46 


Acid  salts 47 

Acidity  of  bases    ...    46 

Acids,  basicity  of    .  .   45 

classification  of    .    43 

defined 40 

formation  of  .       .44 

meta 44 

naming  of   ....   41 

ortho 43 

sulphur,  etc.  ...    49 
Action,  chemical,  in- 
tensity of 78 

Adhesion 2 

^Ether-energy  ....  6 
Air,  composition  of  .  179 
Air-unit,  relation  of, 

to  H  unit 90 

Albite 262 

Aldehydic  acids  of 
phosphorus    ....  209 

Alkalamide 50 

Allotropism 110 

Alum 261 

Aluminates 261 

Aluminum 259 

Aluminum-bronze  .  .  260 
Aluminum  chloride  .  260 

fluoride 261 

hydrates 261 

oxide 261 

phosphate   ....  261 

silicates 262 

sulphate 261 

Alunogen 261 

Amalgams 315 

Amblygonite 327 

Amic  acids 52 

Amid-hydrates .  ...  52 
Amide  defined  ....  50 
Amine  defined  ....  50 

Ammonia 185 

critical  temp,  and 

pressure  of ...  7 
Ammonia  type  ...  50 
A  mmonias,  derived  .  50 
Ammoiiio  -p  1  a  t  i  n  i  c 

bases 276 

Ammonium 328 

amalgam 328 

aurate 307 

carbamate  ....  329 
carbonate    ....  329 

chloride 328 

nitrate 326 


Ammonium  sulphate,  328 
Ampere's  law  ....  12 
Analogues,  atomic  .  .  26 

Analysis 9 

Analytical  reactions  .    70 

Anglesite 267 

Anhydrides    .       ...    43 

Anhydrite 323 

Animal  coal  .  ...  226 
Annabergite  .  ...  294 

Antimony 215 

Antimonic  oxide  and 

acid 217 

Antimonous    oxide 

and  acid 217 

Antimony  sulphides  .  217 

Apatite 323 

Aphthitalite 332 

Aqua  fortis     .   .   .   .  .  192 

Aqua  regia 193 

Aragonite 323 

Argand  burner ....  244 

Argentite 302 

Arsenates 214 

Arsenic 210 

Arsenic  oxide  and 

acid 213 

Arsenites  .  .  .'  .  .  215 
Arsenous  oxide  and 

acid 214,  215 

Arseno-pyrite    ....  210 

Arsine 211 

Artiads 20,  21,  38 

Asbolite 295 

Atmosphere 178 

Atom  defined  .  .  .  .  2, 14 

Atomic  analogues  .  .   26 

attraction    ....     3 

group,  calcul'n  of    84 

heat 17 

masses  .  .  5,14, 16, 17, 
27,83 

notation 27 

symbols  .  .  .  .  27,  28 
valence,  how  indi- 
cated   27 

Atomicity  of  mole- 
cules   13 

Atoms  classified  ...  14 
combin'g  power  of,  18 
exchange  of  ...  36 
in  H  molecule  .  .  12 
in  elemental  mol- 
ecules   13 

(343) 


344 


INDEX. 


Atoms,  multiplication 

of 28 

naming  of  ....    11 

valence  of  .  20,  21,  22 

variation  in  .    38 

Attraction,  atomic  .  .     3 

mass 2 

molecular   ....     2 

Aurates 307 

Auric  chloride  ....  306 

oxide 306 

Aurous  chloride  .  .  .  306 

oxide 307 

Aurum  musivum  .  .  267 
Avogadro's  law-  ...  12 
Azurite 302 

Barite 325 

Barium 325 

chlorate 325 

chloride 325 

di-oxide 325 

hydrate 325 

nitrate 325 

oxide  ...•    ...  325 

sulphate 325 

sulphide 325 

Bases,  acidity  of   ...   46 

denned 40 

naming  of  ....   41 

ortho  and  meta  .   45 

sulphur,  etc. ...   49 

Basic  hydrogen    ...   45 

salts 48 

Basicity  of  acids  ...   45 

Beryllium 325 

aluminate  ...     261 

Berthierite 218 

Berthollet's  laws .  .  72,  73 
Bessemer  process  .  .  288 
Binaries,  formation 

of 35,36 

notation  of  .  .   .  .   34 

Binary  molecules    .  .    32 

naming  of  ....    32 

terminations    .  32,  33 

Bismite 218 

Bismuth 218 

Bismuth  ates 220 

Bismuth  carbonate     .  220 

nitrates     220 

oxides  of 220 

phosphate   ....  220 

sulphate 220 

sulphide 220 

Bismuthic  acid    ...  220 

Bismuthinite     .  ..    .   .  220 

Bismuthous  chloride  219 

oxide  and  hydrate  220 

sulphide 220 

Bismuthyl  chloride    .  219 

Bismutite 218 

Blende 313 

Blue  vitriol 301 

Boiling  point     ....     6 

Bonds 28,  31,  35 

Boracite 257,  319 

Borax 259 


Boric  acid 258 

oxide     258 

Bornite 299 

Boron 257 

Boulangerite 218 

Brass 300 

Brimstone,  roll     .   .   .151 
Britannia  metal  .  .   .  265 

Bromine 116 

acids  of 148 

oxides  of 148 

Bromyrite 302 

Brongniardite   ....  218 

Bronze 265 

Brucite 319 

Brushite 324 

Bunsen  burner     .   .   .  244 

Cadmium 314 

Caesium 336 

salts  of 336 

Calamine 313 

Calcite 323 

Calcium 321 

carbonate    ....  323 

chloride 322 

hydrate 322 

oxide 322 

phosphate  ....  :->2l 

sulphate 32;; 

Calculations  founded 

on  mass 79 

of  percentage    .  .   80 
from  equations,  85,  88 

Calomel 316 

Candle-flame 246 

Carbon 224 

Carbonates 240 

Carbon  di-oxide  .  .  .  2:;r> 
di-sulphide  ...  248 
mon-oxide  ....  211 
thermo-chemistry 

of 2M 

Carbonic  acid    .  .  .  .  240 

Carbonyl 241 

chloride 242 

Carnallite 332 

Cassiterite 266 

Cast  iron 286 

Celcstite 324 

Cementation 288 

Cerargyrite 304 

Cerussite 267 

Cervantite 216 

Chalcocite 302 

Chalcopyrite  . ' .  .  .  .299 

Charcoal -226 

Chemical  action,  in- 
tensity of     78 

modes  of 74 

Chemical  changes  .  4,  80 
change,    condi- 
tions of       ...   71 
mass  in    ...    80 
equations    ....    69 

reactions 68 

relations  of  work 
and  energy  ...   75 


Chemical  properties  .     4 
Chemism     ......     3 

Chemistry  defined  .  .     5 
province  of  ....     3 

thermo-    .....     5 

Chloric  acid   .  .....  147 

Chlorine  .......  107 

acids  of    .....  145 

allotropism  of  .  .110 
oxides  of  .....  145 

sulphides    ....  171 

tetr-oxide    ....  146 

Chlorous  oxide  and 

acid    ......  146 

Chloro-platinates    .   .  276 
Chrome-alum    ....  281 

Chromic  acid    ....  280 

chloride   .....  278 

hydrate    .....  281 

oxide     ......  280 

per-fluoride    ...  279 
tri-oxide  .....  279 

Chromite     ......  278 

Chromites  ......  2SO 

Chromium  ......  278 

sulphate  .....  281 

Chromous  chloride    .  279 
oxide     ......  281 

Chromyl  chloride    .  .  281 
Chrysoberyl   .....  259 

Cinnabar  .......  317 

Classification  of  acids  -i:> 
of  atoms  .....    20 

of  molecules  .   .31,  -19 
of  ternaries    ...    39 
of   ternary  mole- 
cules united  by 
nitrogen     ....  49 

Clausius's  hypothesis   til 


Cla 


-J62 
226 
226 

.  226 
233 
29  1 

.  295 
295 

.295 
29:. 

.  295 
2 


lay 
Coal,  animal 

mineral 

vegetable    . 
Coal-gas 
Cobalt 

Cobaltamines    . 
Cobaltite 
Cobalt  chlorides 

oxides 

Cobaltous  salts 
Cohesion 
Colcothar    ......  291 

Combination  by  vol- 
ume   .......  60-66 

Combining  power  of 
atoms    .......   17 

modification      in 

rule  of  .....  36 
Combustibles  ....  243 
Combustion  .....  242 
Comp.  ammonias  .  50,  51 

radicals    .  .   .   .37,38 

Construction  of  equa- 
tions ........    70 

Converter,  Bessemer  .  288 
Corundum  ......  259 

Cotunnite    ......  269 

Covellite  .......  302 


INDEX. 


345 


Critical    temperature 
and  pressure  ....     7 

Crocoite 278 

Crocus 291 

Crookesite 309 

Cryolite 259 

Cupric  carbonate    .  .302 

chloride 301 

hydrate     .....  301 

nitrate 301 

oxide 301 

phosphate    ....  302 

sulphate 301 

sulphide 302 

Cuprite 299,  30*2 

Cuprous  chloride    .   .  301 

hydride 301 

oxide 302 

sulphide 302 

Cyanite 255 

Cyanogen 249 

Deliquescence  ....  141 

Density 2,  56 

absolute 2 

relative 2 

rel.  of  volume  to  .  89 
rel.  of,  to  sp.  gr.  .  90 
periodicity  of  .  .  24 
rel.  mol.  mass  to  .  56 

Diamine 189 

Diamond 224 

Diaspore 259 

Diffusion,  gaseous  .   .    58 

law  of 58 

explanation  of  .   .   r>9 
det.  mol.  mass  by,   59 
Di- hydrogen  di- car- 
bide     232 

Dimorphism 152 

Direct  union 42 

Di-sulphuric  acid    .   .  108 
Di-thioiiic  acid     ...  170 

Dolomite 319 

Double  salts 48 

Dyads,  ternaries  unit- 
ed by 39 

Dyscrasite 216 

Effervescence    ....    73 

Efflorescence 141 

Electricity 6 

Electro  -  chemical  se- 
ries   19 

Elemental  groupings    23 
Elements,  periodic 

law  of 25 

periodicity  in 
properties  of  .   .    23 

*  Embolite 302 

Emery 261 

Empirical  formulas    .    48 

Emplectite 220 

Energy  and  work, 
chemical    relations 

of 75 

Equations,  chemical  .    69 
construction  of    .    70 


Equations,    calcula- 
tion from    ....  85,  88 

rule  for  writing    .    69 

simult.  linear    .   .    70 

Erbium 325 

Erythrite 295 

Etching  glass  ....  122 
Ethiops  mineral  .  .  .  317 
Ethylene 231 

crit.  temp,  of  ...     7 
Eudiometer,  Ure's  .  .  138 

Volta's 181 

Exchange  of  atoms  in 
forming  binaries  .   .    36 

Factors  equal  to  prod- 
ucts     69 

Ferric  acid 290 

chloride 289 

di-sulphide     .  .  .293 

hydrates 291 

oxide 290 

tri-oxide 290 

Ferrites 291 

Ferrous  carbonate  .   .  292 

chloride 290 

oxide 292 

sulphate 292 

sulphide 293 

Ferroso-ferric  oxide  .  291 
Flowers  of  sulphur  .  150 

Fluorine 119 

Fluor  spar  ....  119,  321 

Formation  of  binaries   35 

meta-acids  ....    44 

molecules    ....   31 

salts 46 

ternaries  .   .   .   .  42,  43 
Formulas,  binary    .   .    34 
calculation  of    .  .    82 
empirical  and  ra- 
tional     48 

of  salts     46 

use   of   numerals 

in 34 

Fowler's  solution   .  .  215 

Franklinite    .   .  .  .   .  292 

Fusible  metal  ....  219 

Lipowitz's   ....  219 

Rose's 219 

Gahnite 261 

Galenite 267 

Gallium 308 

chlorides 308 

oxide     308 

nitrate 308 

sulphate 308 

Galvanized  iron  .  .  .  :U2 

Gas-carbon 226 

Gaseous  change,  law 

of 72 

diffusion 58 

volumes,  r  e  d  u  c- 
tion  of,  for  tem- 
perature  ....    91 
for  pressure    .   .    90 
Gay-Lussac's  law    .   .    60 


Germanium 272 

German  silver  .   .  301,  312 

Gersdorffite 294 

Gibbsite 261 

Glass,  crown  ....  255 

flint 255 

soluble 255 

Gold 305 

chlorides 306 

fineness  of  ....  306 
oxides  ....  306,  307 

GSthite 291 

Graham's  law  of  dif- 
fusion     58 

Graphic  symbols  ...    28 

Graphite 225 

Gravitation 2 

Greenockite 314 

j  Group,  atomic  ....    84 

halogen 123 

Groupings,  elemental  23 
Gypsum 323 

Halite 329 

Halogens 123 

Haloid  salts 123 

Hausmaunite    ....  282 

Heat 3 

atomic 17 

of  liquefaction  .   .     6 
of  vaporization .   .     6 

specific 6 

Heat-unit  ...  6, 103,  246 

Heavy  spar 325 

Hematite 291 

Hydrazoic  acid ....  189 
Hydrocarbons  ....  228 
Hydrobromic  acid  .  .  120 
Hydrochloric  acid  .  .  112 
Hydrofluoric  acid  .  .  121 
Hydriodic  acid  ...  121 
Hydrogenium  ....  105 

Hydrogen 99 

acid 46 

basic 45 

molecule 12 

Hydrogen  arsenide    .  211 
antimonide    ...  216 

bromide 120 

carbide 228 

carbonate    ....  240 

chloride 112 

di-carbide   ....  231 

fluoride 121 

iodide 121 

nitrate  190 

nitride 185 

oxide 136 

peroxide 143 

phosphate  ....  206 
phosphide  ....  203 

silicate 254 

silicide  .  .  .  .  .  .252 

stannate  .....  266 

sulphate 162 

sulphide 154 

sulphite 159 

Hydromagnesite  .   .  .  321 


346 


INDEX. 


Hydroxide  41 
Hydroxyl                  38  143 

Liquor  fumans  Liba- 
vii                              .  265 

Matter  and  energy  .  .     5 

Hydroxylamine   .   .  '.  189 
Hypochlorous     oxide 
and  acid  145 
Hyponitrous    oxide 
and  acid  198 
Hypophosphorous  ox- 
ide ...  209 

Litharge  271 
Lithium  327 
carbonate    ....  327 
chloride   327 
hydroxide  ...   ,327 
oxide     327 
phosphate  ....  327 

divisions  of    ...     2 
compoimd  ...     9 
elementary.   ...     9 
physical  states  of,     6 
heterogeneous  .  .     3 
homogeneous    .  .     3 
how  studied              1 

Hyposulphurous  acid  157 

Ice,  artificial    .  .  167,  188 
Illuminating  gas  .   .   .  23:3 
Imides               •          •   51 

sulphate  327 

Magnesia  alba  ....  321 
Magnesio-ferrite  .   .   .292 
Ma°nesite    ...      .     3*21 

motions  of  ....     3 
Melaconite  ....  299,  301 
Melanterite    292 
Melting  point    ....     6 

Indium     308 

Magnesium    319 

iodide                      316 

chloride       ....  309 
hydrate        ....  309 

aluminate   ....  261 
carbonate    ....  321 

nitrates     ....     317 
oxide                        317 

oxide  309 
sulphate      ....  309 

chloride   320 
hydrate    320 

sulphates     .   .   .  .317 
sulphide  317 

sulphide      ....  309 
Intensity  of  chemical 

oxide     320 
sulphate  320 
Magnetism                       6 

Mercurous  chloride  .  316 
iodide    317 
oxide                       317 

lodic  acid    149 

Magnetite   291 

sulphide  317 

Iodine                            117 

Malachite                       302 

oxides  and  acids 
of    148 

Malleable  iron  ....  289 
Manganese  281 

specific  heat  of  .  .     7 
Mercury  amides           318 

Iridium    277 
Iron    284 

chlorides  282 
di-oxide  284 

Meta-acids  44 
formation  of             44 

metallurgy  of,  285,  280 
chlorides  .  .   .289,  290 
oxides               290  292 

Manganic  acid  ....  283 
oxide     2s:: 
tri-oxide                  282 

Meta-elements         .   .   11 
Meta-phosphoric  acid,  207 

Jamesonite  218 

Kaolin  262 

Kelp                                 117 

Mangauite  28-1 
Manganous  carbon  a  te,2.s  1 
oxide  284 
silicate  284 
sulphate  284 

Mehithetical  reaot'ns,    70 
Meteorites,  hydrogen 
in     99 
Methane  228 
critical  temp  and 

Kobellite     220 

Labradorite  ...  255,  262 
Lampblack     227 
Larderellite                  257 

Marcasite    293 
Marsh-gas    228 
critical  temp,  and 
pressure  of  ...     7 
Marsh's  test    212 

pressure  of  ...     7 
Metric  system    ....  :',;;'.» 
Miargyrite  .  .   -     21S,  :>,02 
Mimetite  267 
Mineral  coal  226 

Laughing  gas    ....  199 
Law  of  Ampere    ...    12 
Law  of  Avogadro    .  .    12 
combination     by 
volume           .  .   60 

Mass,  atomic  .  .  .  .  14,  57 
how  fixed  .  .  14,  15,  17 
relation  of  densi- 
ty to  56 
relation  of  diffu- 

waters     142 
Mirabilite    331 
Mispickel     210 
Modes  of  chemical 
action    74 

diffusion                    58 

sion  to  58 

Molecular  attraction       2 

gaseous  change   .   72 

calcula'n  founded 
on       79 

mass  .  12,  31,  56,  59,  83 
det  by  diffusion       59 

Law,  p'eriodic   ....   23 
thermo-chemical  .    76 
Laws  of  Berthollet    71  72 

concerned    in 
chem.  changes  .   80 
definitions  of    .  .     2 

Molecular  mass,  rela 
tion  of,  to  density       56 
motion  3 

Lead               207 

Mass,  molecular  ...   31 

stability    ....       68 

action  of  water 
on       268 

fixed  by  density  56 
rel.  of,  to  den- 

symbols   ....       28 
volume  56 

alloys  of                  269 

sity  56 

Molecule,     definition 

chlorides                 269 

of        .   .                      29 

oxides                     270 

ecules    .      ...    12 

formation  of  ...    31 

Leaden-chamber  proc- 
ess    162,  165 
Leblanc  soda  process,  331 
Lepidolite               255  327 

relation  of,  to  vol- 
ume        89 
Mass-attraction     ...     2 
Mass-motion             .         3 

Molecules,    atomicity 
of     13 
binary   31,32 
classification  of,  9,  31 

Leuco-pvrite     .  .        -210 

Masses   atomic,  table 

compound  .   .   .  9,  31 

Libethenite    302 
Light     6 

of     16 
repr  by  symbols  .    27 

differences  in    .   .     4 
elemental  ...     9-13 

Lime  322 

of    factors    and 

multiplication  of  .    28 

Limnite    .   .                 .  291 

products  equal  .    69 

ternary    .   .   .   .  39,  49 

Limouite  .    .              ,   .  285 

Massicot   .                 ,   .  271 

unsatu  rated    ...   37 

INDEX. 


347 


Morenosite  294 
Motion,  atomic    ...     3 

Phosphoric  acids,  al- 
dehydic    209 
oxide            .          .  205 

Properties,  periodic   .    23 
prediction  of  ...    26 
Pyrargyrite             218  302 

molecular    ....     3 
Multiplic'n  of  atoms  .    28 
of  molecules  ...   28 

Names    of   elements 

Phosphorous  oxide    .  209 
Phosphorus    200 
red  203 
oxides  and  acids 
of     205 

Pyrite    293 
Pyrolusite    284 
Pyromorphite   ....  267 
Pyrophorus    269 
Pyrophosphoric  acid  .  208 

derivation  of  .   .  .   .342 
Naming  of  acids  bases, 

Phosphorus  bronze    .  301 
Photometer   .   .   .  236,  246 
Physical  changes     .  .     3 

Quality  of  combining 
power    17 

binary  molecules,   32 

properties    .  -   .  .     4 
science     1 

Quantity  of  combin- 
ing power  ...      .18 

elem.  molecules  .    11 
Natural  waters  .   .   .   .142 

Physics,  province  of  .     3 
Pig  iron    286 
Plaster  of  Paris              3''3 

Quartation  306 
Quartz  253 
Quicksilver                   314 

Niccolite                        294 

Platinum     274 

Nickel    293 

black  276 

Radicals,  comp.  .  .  38,  39 

Niter  335 
Nitric  oxide  190 
acid    190 
Nitriles  51 
Nitrogen  176 
oxides  and  acids 
of     189 
di-oxide                   195 

chlorides  276 
oxides   276 
spongy  274 
sulphides    .  .  .  .276 
Plumbates  270 
Plumbic  carbonates  .  271 
chloride   269 

artiad  and  peris- 
sad  38 
Rational  formulas  .  .    48 
Reactions,  chemical,  68,69 
always  molecular,   68 
classification  of    .   70 
expressed  by  for- 
mulas                   68 

tetr-oxide                193 

nitrates                  •  271 

Re-agents    68 

Nitrosyl                          196 

Realgar               .            210 

Nitrous  oxide  and 
acid    194 

perchloride    .  .  .270 
peroxide  270 

Red-leads    270 
Red  precipitate    .   .   .  317 

Normal  salts  47 
Notation,  atomic  ...    27 
of  binaries      .          34 

sulphate  271 
Plumbous  oxide  .  .  .  271 
Pollucite                       336 

Reduction  of  gas  vol- 
umes  for  pressure 
and  temperature    90  91 

Number  of  bonds           31 
of  perissad  atoms,    31 
Numeral  prefixes    .  .   34 
Numerals   in   formu- 
las       34 

Positive  atoms  ....   17 
change  in  termi- 
nation of  .   ...   42 
Potassa-niter  or  salt- 
peter    335 

Refraction  equivalent, 
periodicity  of    ...   24 
Relations  of  work  and 
energy  75 
Rhodium                       277 

Olefiant  gas    .....  231 
Orpimcnt        .                210 

Potassio-aluminum 
sulphate  261 
Potassium                      332 

Rinman's  green  ...  296 
Rock  crystal  .       .   .   .  253 
Rouge                             291 

Ortho-acids     43 

aluminate   .  .        261 

Rubidium                      335 

Orthoclase  262 

bromide   334 

carbonate    .  .  .     336 

Ortho-stannic  acid  .   .  266 
Osmium    277 
Oxygen     126 

carbonates  ....  335 
chlorate    334 
chloride                   333 

chloride    336 
nitrate  336 
sulphate                  336 

critical  temp,  and 
pressure  of  .   .7,  128 

chloro-chromate  .  281 
di-oxide                   334 

Rule  for  naming  bina- 
ries                               32 

Ozone    131 

hydroxide   ....  334 
iodide    .  .      .        334 

Ruthenium    277 

Palladium  277 
Paris  green  -.  215 

nitrate  335 
oxide  .                     334 

Safety-lamp    245 
Sal-ammoniac               328 

Penta-thiouic  acid  .   .  170 
Percentage    composi- 
tion        80 
Perchloric  acid  ...    148 
Periodic  law  ....  23-27 

plumbate     ....  270 
sulphate  335 
tetr-oxide    ....  334 
Power,  combining,  of 
atoms                        17  18 

Saline  waters  142 
Salt  defined    40 
Salts,  acid   and   nor- 
mal         47 

Periodicity  in  proper- 
ties of  elements    .       23 

Precipitant  72 
Precipitate                      72 

derived  from  bases,  47 

Perissads  .   ...  20,  21,  38 
Permanganic  acid  .  .  282 
oxide                        289 

Precipitation  72 
Prediction  of  proper- 
ties                              26 

formulas  of        .   .    46 
haloid    123 

Petalite    327 

of  results                  73 

sulphur  etc              49 

Petroleum  series  .  .  .  230 

Prefixes,  numeral   .   -   34 

Sassolite   257 

Pewter  265 

Pressure  critical     .         7 

Science                             1 

Phosgene  gas        .        242 

Products  and  factors 

Phosphine  203 

equal  69 

physical             •  .     1 

Phosphoric  acid  ...  206 

of  combustion  .  .  245 

Selenite    323 

348 


INDEX. 


Selenium 171 

Seiiarmontite    ....  217 
Series,  electro  -  chem- 
ical  19 

homologous    ...    36 

Siderite 285 

Signs  in  equations  .   .    69 

Silicates 255 

Silicic  acid 254 

oxide 253 

Silicon 251 

bronze 301 

Silver 302 

chloride 304 

di-oxide 305 

hydrate 304 

nitrate  304 

nitride 304 

oxide 304 

phosphate   ....  305 

sulphate 305 

Simultaneous     linear 

equations 70 

Size  of  elemental  mol- 
ecules     12 

Smaltite 295 

Smithsonite 313 

Snow  crystals    .       .   .  140 
Soda-niter  or  saltpe- 
ter    332 

Sodio-alumiuum  chlo- 
ride     261 

Sodium C29 

aluminates ....  261 
bismuthite  ....  220 
carbonates  ....  331 

chloride 3:50 

hydroxide  ....  330 

nitrate 332 

oxide 330 

peroxide 331 

phosphates ....  332 

sulphates 331 

Solubility  table    .   .  .  H 11 
Solvay  soda  process  .  331 
Specific  gravity,  rela- 
tion of,  to  density  .   .  90 

heat 6 

Specular  iron     ....  290 
Speculum  metal  .  .   .  265 

Sphalerite 313 

Spinel 259,  261 

Spodumeue 327  I 

Stability,  molecular  .   68  I 
Stannic  acids    ....  266  I 

chloride 265  | 

oxide 266 

sulphide  ....     267 
Stannous  chloride  .   .  266 

oxide 267 

Steam 140 

Steel 287 

Stephanite 302 

Sterro-metal 300 

Stibine 216 

Stibnite 217 


Stoichiotnetry   ....    68 

Strontianite 324 

Strontium 324 

chloride 324 

di-oxide 324 

hydrate 324. 

nitrate      324 

oxide 324 

Substitution 43 

Sulphates 168 

Sulpho-carbonates  .  .  249 
Sulpho-carbonic  acid,  249 
Sulpho  -sulphuric 

acid 170 

Sulphur 149 

flowers  of    ....  150 
oxides  and  acids 

of 157 

Sulphuric   oxide    and 

acid 162 

Sulphurous  acid  .  .   .  159 

oxide  ' 158 

Sylvite 332 

Symbols,  atomic  .   .  16,  27 

graphic 28 

Synthesis 9 

Synthetical  reactions,    70 

Table  of  atomic 
masses 16 

electro- chemical 
series 19 

molecular  struct- 
ure   52 

ortho  and  m  e 1  ;i 
acids  .   .^.   .   .   .    45 

periodic  law  .   .   .    25 

valences 21 

Tellurium 172 

Temperature,  reduc- 
tion of  gaseous  vol- 
umes for 91 

critical 7 

Terminations,  binary,  ::2:: 

Ternary  molecules,  39,  42, 

49 

classification  of    .   39 

formation  of  ...    42 

Tetrad  y  mite 218 

Tetrahedrite 299 

Tetra-thionic  acid  .  .  170 
Thallic  sulphate  .  .  .310 
Thallium 309 

chlorides ...      .310 

oxides 310 

Thallous  sulphate  .   .  .310 

Thenardite 331 

Thenard's  blue  ...  296 
Thermo-chemistry  .  .  5 
Thermo-chem.  laws  .  76 
Thermometer  tables  .  340 
Thionic  acids  .  .  .170 
Thio-sulphuric  acid  .  170 

Tin 264 

Tin  oxides 266 

salts 266 


Triphylite 327 

Tri-thionic  acid  .   .   .  170 

Trona " .   .329 

Turpeth  mineral .   .   .317 

Type,  ammonia    .   .       50 

water 41 

Ullmannite 294 

Unit,  relation  of  the  H 

to  the  air  unit  ...  90 
Units  of  attraction  .  .  31 
Unsaturated  mole- 

cules 37 

Valence 20,  22 

hovy  indicated  .   .    27 
periodicity  of    .   .    24 

table  of     21 

variation  in   .   .  20,  38 

Valentinite 217 

Variation  in  valence, 

20,38 
Vegetable  coal ....  226 

Ventilation 246 

Vermilion 317 

Vitriols 169 

Volume,  atomic   ...    24 
periodicity  of,    24 
combination  by,  60-66 
molecular   .  .      .56 
relation  of,  to  den- 
sity  89 

relation  of  mass  to,  89 
Volume  calculations  .  88 

Wagnerite 319 

Water    . 136 

critical  temp,  and 

pressure  of ...     7 
of  crystallization .  141 

type 41 

Waters,  mineral    .   .   .142 

Wernerite 255 

White  precipitate    .   .  318 

White  vitriol 313 

Willemite 313 

Witherite 325 

Wittichenite 220 

Work  and   e  n  e  rgy, 

chemical  relations  of,  75 
Wrought  iron  ....  286 

Xanthosiderite  .  .      .  291 

Zaffre 296 

Zaratite 294 

Zinc 311 

aluminate   ....  261 
carbonate    ....  313 

chloride 313 

hydrate    .   .       .   .  313 

oxide 313 

silicates 313 

sulphate 313 

sulphide  313 

Zincite 311,  313 


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